If the pool is important, the CBR offers the best pool area IMO for young children. It is zero entry, has two slides that your 4 year old might do well with. They aren't the quickest or longest in WDW. There is also a gated height limit enforced (48 inches) water play area for the kids. It has multiple small slides, quite appropriate for the 2 and 4 year old, and water features. The water in that area is very shallow, great for the baby. Our boys loved it! We loved the locked gate so that we could relax and let our boys run around and have some independence.
The worst pool area IMO for young children is CSR. The pool is deeper than the other moderates in more areas, no zero entry, the slide is long, enclosed, and quick, and the kids play area was quite pitiful. We loved this resort but we won't return until our boys are older.
POR and POFQ are nice as well. FQ is more compact and a bit easier to get around.