Easily #1.
Scrap #2. Do not use your the wireless capabilities of your modem / wireless gateway with a separate wireless router and access points. Unless your modem is in bridged mode (and thus not serving wireless connectivity), it is also acting as a router and wireless access point. Then the wireless router will create its own internal network which the wireless access points will connect to.
Under diagram #2, the network will look like this:
Internet
|
98.21.22.33
Wireless Modem
192.168.0.1
|
192.168.0.254
Wireless Router
192.168.1.254
|
192.168.1.1-253 range
Wireless APs and Clients
You're creating a double-NAT by using both the wireless modem and wireless router in their standard configurations, which can cause connectivity issues for certain applications and services.
Under diagram #1, your network looks like this:
Internet
|
Wireless Modem (in bridged mode)
|
98.21.22.33
Wireless Router
192.168.1.254
|
192.168.1.1-253 range
Wireless APs and Clients
No more double-NAT. If you find connectivity in the main building is still weak, I presume the little grey box is your switch, run a network cable and add another access point to the right side of the Building C basement.