here's my take on it, and there are some resorts I don't know about so I'm sure I'll miss some.
The CR has a small area with some water spraying/shooting equipment that kids can squirt, run through, etc.. , nothing elaborate and no pooling water. It is separate from the pool itself kind of behind the waterslide IIRC
The WL, GF, and POFQ have fun themed splash areas that have a small-ish central tower with 2 low slides coming from it, a small dumping bucket above it, and shallow pools of water around it with spraying water that are zero entry. They are fairly strict on a 48" height limit on the slides, taller kids might be able to hang out but not slide.
The Poly has a much larger, elaborate play area with one medium slide all ages can go down and one small slide for only under 48", more stairs/walkways to play on and squirt water from, and the pooling water gets deeper - but still only to maybe 1.5-2 feet. But deep enough IMO you really have to watch kids that aren't great swimmers or are still young, and it's larger so you can't stand in one area and always see them, they can get behind, etc.
AKL Kidani village has a splash area that I'm not as familiar with, I think it doesn't have slides but does have more water spraying and is much larger and more elaborate than the one at the CR. I don't think AKL Jambo house has anything other than a zero entry pool, but I'm not completely sure.
Pop has a traditional kiddie pool, small, round, and shallow. Last I knew this is what POR had as well, unless they got rid of it.
YC and BC have a shallower, sand bottom part of the main pool with a sand bar in the center where kids can sit and play with buckets, etc, but that part of the pool also gets to maybe 3-ish feet deep in certain parts. There is also a smaller pool across the main walkway that has very small simple water slides, but they go into a few feet of water so not good for true toddlers IMO. AFAIK there is nothing at the BC/YC I would actually call a splash pad.
There is something at AOA, but I haven't stayed there only looked around so I can't remember details. I don't know about the All Stars, any of the straight DVC resorts, the CBR or CSR. When I last stayed at CS and CBR they didn't have splash pads and I can't remember kiddie pools, but that's been a long time so it could have easily changed given all of their renos.