When my kids were approximately the same as the OP, we would do SAB in sections. Here is what we did which could work for the OP.
When parents were not going into the pool and were lounging, the kids stayed in the shallowest sand bottom pool area and did castles and swimming games or played on the small playground and wading pool. They ended up playing mermaids or sand bakery or other games in that area for HOURS

. Generally speaking we could watch that entire pool area from our front row chairs and feel good about their safety. I always felt like there was no better
DVC pool option for small kids than this section of SAB. YMMV.
When parents had rested up a bit (and had an umbrella drink or two) we went as a family to the other parts of the pool. We enjoyed the sinking sands, the pool games and DJ, the lazy river, the whirlpool area, etc. I also feel like there is no better DVC pool option for families than these sections of SAB. Again YMMV.
We also did the slide, and I understand the OPs hesitation to send DD by herself. My main concern is definitely the out of control surrey bikes being peddled by four crazies honking the horn and yelling for everyone to get out of the way. This doesn't happen all the time by any means, but it does happen often enough. Throw in a golf cart or two while a leaf blower is howling and you can't hear very well, and it can be a little chaotic. It isn't a big deal at all if I'm there to help guide DD, but I'm a little uncomfortable with her on her own.
I agree with the PP about splitting up parents. You don't need to do the slide all day and be split up. Just take 15-20 minutes and allot that to slide time. You can have one parent stay in the small pirate play area below the staircase with the other kids. They will have their own smaller slide and get to swim inside a cool pirate ship. Have the other parent wait at the Flying Jib exit and make sure DD emerges in tact. You can walk her back to the pirate ship where the other parent is waiting and do it all over again. Great memories and the best slide at WDW IMHO of course.
Hope you have a great trip wherever you decide

.