So, you're a family of 3, and possibly 4 at some time in the future. Your current child is young. You could really have any resort as your home resort. But, you asked about PVB...
The Poly is a lovely resort with a great pool. While you can now walk from MK to the Poly, it's a very long walk. Plan on taking the Monorail to the MK and Epcot. The studios, having been converted from hotel rooms, are large (although not quite as large as OKW). Booking at 7 months during the summer, until this year, hasn't been an issue. Unless you own at Poly, don't expect to get a room there at the 7 month window for Easter, Jersey week, or any week between September and mid January. Points needed to book a studio are on the higher side.
Also on the monorail loop is BLT. BLT shares a lot of amenities with the Contemporary. BLT has an ok pool dedicated to itself, and you can also use the Contemporary pool if you desire. You can easily walk (about 6 minutes) from BLT to MK, and there's a dedicated security checkpoint there so you don't have to deal with security again. This is a great advantage if you are travelling with small children in a stroller. Of course, you could also take the monorail. Studios are a little small, but fine for 2 adults and 2 small children (or one larger child). Points needed to book a studio are lower than at Poly. There's also awesome theme park view rooms, where you get a great view of the park, and your young children can watch the fireworks from just before you force them to go to sleep. You can generally book lake view rooms at 7 months during the summer. Again, you may have problems booking at 7 months for Easter, Jersey week, or any week between September and mid January.
Also in the MK area is CCV/BRV. BRV expires in 2042. It's an option if you think you'll keep your
DVC membership until the kids go to college. CCV is at the same location, but with a longer expiration date. CCV is likely a better option if you think you'll be holding the membership for more than 20 years. You'll take the boat to the MK, which is fine during the summer, but can be awfully cold in the winter or at night. Everywhere else, it's a bus ride. Booking CCV/BRV has the same issues as Poly and BLT during those peak periods. Point requirements for a studio are lower than Poly, and similar to BLT.
My wife and I love the Poly, and stayed there about 20 times in the hotel side, but didn't like the placement of the DVC buildings there. They're near the TTC boat launch, and the Ferry horn goes off all day and quite late at night (1 hour past MK closing and 1 hour before opening, which means 7-8am start to 1am end during the summer). The standard view studios may result in a view of the monorail, which we're not interested in. We live in the Poconos, so BRV/CCV was out (because it's just like home). We rented points at BCV over by Epcot, but decided that we preferred to be near the MK. We then rented points at BLT, and decided that was for us. We would have kept going, renting points at each resort, until we found the right home resort for us. I encourage people to buy where they want to stay, and also to rent points and stay a few nights in your "final" choice just to make sure.