Female mollies (and most other if not all live-bearers) can store sperm for months, so even though one of your fish has already given birth, all three might still.
I would keep the babies separated until they are big enough not to fit in any of the other fish's mouths.
As for special requirements, either a net breeder or a separate tank would work. I'm not the biggest fan of net breeders, but keeping a whole separate tank can be a big hassle since you still need to keep the temperature, ammonia, nitrite, and nitrate in check if you don't want to slow the babies growth.
I live in Morgantown when I'm in WV, but I'm in New York for the summer, and won't be heading back to WV for a few more weeks.
P.S.--I wouldn't be suprised to find a few more babies over the next week, I noticed that my babies had a tendency to hide in the substrate while they could fit between the pieces of gravel.