It sounds like a pretty fun game and something I would enjoy to play!
There a couple of things I would change. For example, I have had UNO games where some people have 10+ cards when someone wins and I think that 10+ diapers in one single round is a bit too much, so perhaps put a limit or do like “amount of cards/3” or someting like that.
I would also put some extra rules at the “change of color = drink water” because it would be a bit too much. Perhaps do something like spin a bottle and the pointed player drinks (or if there are a lot of playes, the pointed and the two adjecent ones).
(Then this is a personal preference) The baby talk. First of all, as a non native english speaker, baby talk confuses me a lot, so it would be a huge inconvenience for me. Also, if I’m honest, I’m not a fan of baby talk in general
Perhaps the effect can be minimized a bit and be something like “You have to baby talk a sentence once per turn” or “You have to say the name of every card you play in baby talk”, that could be interesting and fun.
Also, I should mention that I studies videogame design and development at university and, even though it was mostly focused on programming, we learned some game design and we started with the design of more basic things like simple tabletop games.
So if you have any question you can always ask me. It might not be as good as a professional’s advise, but I can help with what I can :3