Stay at the Beach Club or YC-- if you like to swim. The pool there is the best on the premises. However, it is spread out, so keeping track of 4 kids may be tricky.
We own at the BWV and I just love the Boardwalk, but the pool at the BC & YC is just awesome. There is a section where the pools bottom is sand and the kids can build sand castles and everything. There is a pretty good slide and a lazy river too. Also, there is a lot to do during the day(hair wraps, picking a pearl out of an oyster, renting boats, music and I think they had movies at the beach in the evenings during the summer.
The BC does quiet down at night but the BW is just a 3 minute boat ride across the lake. The BW comes alive at night with jugglers, magicians and different entertainers. They usually have 2 different ones per night and they do the same show. they have a few carnival type games too and a sweet shop, bakery and ESPN. You can rent surrey bikes too.
Either way you will have a great time!!!!! You can walk over to the bridge and watch illuminations without having to go into the park. But its only a 5 minute walk home from Epcot if you do decide to watch inside the park.
HAVE a great time!!