We were there in Jan, March and June and both my kids had toy floats, the ring kind. I also took along a float lounger for me in June but the Neverland pool is too crowded to use it. I did take it and use it at the cove pool and floated all day long, no crowds there. So based on my experience, I would say yes, you can have toys. My kids had balls too, the water kind and they played that for hours and wore goggles, even down the slide. The only rule they told my dd was no floats down the side!
The lifevests are really nice and there are plenty of them if your kids need one. The thing they run out of are chairs! Usually, you can wait a bit and someone will be leaving though or ask people if they are really using them. We found that a family of four would save 4 chairs, 2 for the kids who never used them and were in the pool the whole time so they would give them to us! The best part though is there are lots of lifeguards so if you blink, you don't have to panic that your kid is out of sight for a minute. There is a lifeguard at the top of the slide too so they make sure it is clear before the next one goes down. There is no lifeguard at the cove pool though. Have fun!