I love Disney World. I've gone three times, and would love to go back any time. One thing to keep in mind is that the place is huge. The land owned by Disney in Central Florida is roughly the size of San Francisco, and the vast majority of it is undeveloped. It can easily take an hour to get from the front gate of one of the parks to the front gate of another.
How old are the people who are going?
Disney has recently converted a bunch of the rooms at the "All Star Music" resort into "Family Suites". The All Stars are basically motels, with exterior hallways and entrances, nothing spectacular, but comfortable. There are three All Star Resorts, each with its own theme, Music, Movies, and Sports.
Each resort is further divided into sections with a sub-theme. The sub-themes are depicted with gigantic (and pretty gaudy) "icons", like a three story tall cowboy boot at the "Country" building at All Star Music. They also have two themed pools at each resort (one is big and loud for the kids, and the other is supposed to be the quiet pool for adults - the one at Music is shaped like a piano).
The Family Suites are in the Calypso section of All Star Music. To make the Family Suites, they took two rooms that had previously been connected with an interior door, removed the interior door and walled-in one of the exterior doors so there's only one entrance. Then, they made one of the rooms into the "parents'" room with a king (or queen) bed and a kitchenette, and made the other room into the "kids'" room, with smaller beds and such. Because they were formerly two separate rooms, each side has its own bathroom area, which will make getting ready in the morning a lot quicker. Here's a description of them:
http://www.mousesavers.com/allstarmusicsuites.html
As it says, you might be better off getting two adjoining rooms for a lower price.
If you decide to go for the adjoining rooms, you can pretty much pick any of the Disney resorts, depending on your budget and which theme you would prefer. There are three levels of resorts at Disney World - Value, Moderate, and Deluxe - and the prices are what you would expect for those levels.
The Value resorts are the All Stars and a larger resort called Pop Century, which features buildings themed to the different decades of the 20th Century. Right now, they've only built the last 5 decades, and there's talk that before they finish the first 5 decades, they'll scrap the whole "decade" idea and make it more of a Disney pop-culture theme. The themes are really unimportant, unless you dream of sleeping in a building with giant statues of Lady and Tramp out in front. Each of the Value resorts has a central building with a small store (for souvenirs and sundries) and a large cafeteria style dining area, the food at Disney World is pretty universal from place to place, so there aren't really any surprises or unique items. There is also a small pool-side bar at each of the resorts.
The Moderate resorts are a step up from the Value resorts and have a little nicer theme tacked on to what are essentially still motel rooms. I stayed at Port Orleans Riverside, which was very nice and has an "old south" style to it. The Moderates also have a cafeteria and store, plus they also have a themed sit-down table service restaurant, with higher-quality and more unique food.
The Deluxe resorts are very nice. They are hotels, so the room entrances are inside the building, and most have balconies to the outside. The themes are much more elaborate and well-executed. The Animal Kingdom Lodge, for example, has its own African Savannah with elephants and giraffes roaming around outside your room.
Like I said, the prices for each level of resort are higher than the last, but the great thing is that there are so many hotel rooms in the Orlando area, that prices are actually quite low compared to most places you would visit. $50 or $60 a night at a Value resort are not unheard of in non-peak times.
With the economy where it is right now, Disney is offering some incredible deals to try to get any occupancy. Before Christmas, they were offering 7 days for the price of 4.
They also offer package deals that are essentially all-inclusives. You get a bus pick-up and drop off at the Orlando airport (a good way for Disney to ensure you don't give any money to Universal or Sea World), hotel, park tickets, and three meals per day for a fixed price.
You can stay off-property for even cheaper than staying on-property, but keep in mind that being off-property pretty much requires a rental car and you'll have to pay for parking at the parks every day (it was $10 4 years ago, so it's probably more now). If you stay on-property, there is a very good free bus system that will take you anywhere you want to go on the vast Disney property. If you do get a rental car and stay on-property, parking is free at all the parks.
I prefer having a car even though it isn't necessary, just because you can feel a little claustrophobic being surrounded by Disney 24/7. Again, like hotel rooms, because there are so many rental cars in Orlando, you can get some great deals if you go in non-peak times.
If you're on-property with a car, I would drive to every park except the Magic Kingdom. The parking lot at the Magic Kingdom is on the other side of a giant lake and the only way to get to park is via either a ferry across the lake or the monorail. Either one will take about 20 minutes to get you to the park gate. The bus from your resort will drop you off just to the side of the gate. The other parks (there are 4 full parks, plus 2 water parks, and Downtown Disney, which is a shopping/entertainment district) all have parking lots that either a short walk or tram ride to the front gate.
Another perk of staying on-property is access to the "Extra Magic Hours". Every day of the week at least one park opens an hour early or stays open two hours later just for people who are staying on-property. This lets you get in a lot more rides in a relatively empty park.
You'll want to give yourselves at least a full week at Disney World if it's your first trip. The Magic Kingdom and Epcot each can take a full two days to see and the Animal Kingdom and Disney Studios are each at least one full day. If you go at a time when everyone else is going, the parks will be crowded, so you'll get to see even less than usual (but the parks are open longer - and if you're from Calgary, midnight in Orlando will only feel like 10pm to your body).
If you don't have to take time off at a certain time because of school commitments, I'd want to go sometime after Easter, but before US Memorial Day (which is one week after Victoria Day), or sometime between mid-October and mid-December (avoiding the US Thanksgiving weekend).
If you have to go at a time when school is out, the last two weeks of August will good for avoiding crowds because a lot of the southern US schools go back around the 15th. Unfortunately, the end of August is hurricane season, and summer weather in Florida is hot and humid. I've been in 85 degree heat in Orlando and 100+ degree heat in Vegas, and much preferred the dry heat in Vegas.
The last two times I went was in January, and the weather down there was fantastic, very similar to early June in Calgary (not too hot yet, but still warm enough to wear shorts or at least jeans and a t-shirt), but it did get pretty cold at night.