main pool at Poly has the new kiddie area. Also, as another post of mine indicates, the quiet pool at Poly opens on the 12th of March. Zero entry pool for a large part of it.
Considering ages- MK is so close with monorail both distance and especially time wise. Even with car driving to MK parking lot, it's a pain from Epcot resort hotels. You can always take bus from BC to MK, but it's usually at least a 30-45 minute trip each way depending upon when you catch the bus in the cycle. Could walk to back entrance of Epcot, proceed to front entrance and catch monorail to TTC and transfer to local resort monorail to MK, but, oh my, that's both a long haul distance and time wise.
Having just come back from 9 days at Poly, it was nice to take monorail to MK and to Epcot. There's no bus service from Poly to Epcot. Must take local to TTC, transfer to monorail to Epcot. Don't think there is bus from either GF or Contemporary either based upon how it is at Poly since you can get to MK via the monorail.