Will your brother have a car?
There are some awesome places off-site that they could stay that have great rates compared to on-site but I usually only recommend off site if you have a car. But that's just me. (Actually, DH and I use the van even when we are on-site) Lots of places to check..........I like the villadirect.com site. YOu can search under all of your criteria. Windsor Palms gets high marks on the "Orlando Hotels" section of this board. If you want to post over there you will get even more info for off-site.
This is a house in WP.........Just check slide show and see every room. This is $160 a night.
http://www.villadirect.com/nvd_summ...Year=2006&dpDay=15&dpMon=2&dpYear=2006&agID=0
Here is a villa, for example, it is $115 a night.
http://www.villadirect.com/nvd_summ...Year=2006&dpDay=15&dpMon=2&dpYear=2006&agID=0
Here is one for $105 a night.
http://www.villadirect.com/nvd_summ...Year=2006&dpDay=15&dpMon=2&dpYear=2006&agID=0
These are just a few examples of thousands of places. WP is close to the parks as are many other developements.
And then there is always the timeshare route.......renting one of those. You can usually find a two bedroom for under $100 a night, but you might want a three bedroom............how old are the children? That would make a difference.
Just let me know if you need more info for off-site.
If they want to stay on site, the cheapest option is two rooms at a value resort ($154-$218 a night depending on when in Feb. your brother is going) and that would give you two bathrooms............that's a must.

Two rooms at a moderate would work also(at least $268 a night).
Oh, I forgot about Ft. Wilderness Cabins............depending on how many fit in there. That would be like $239 or something.