First off, the theme is adorable. Genius move to have the consequence of losing being a bad sunburn. Perfect for your target age range. After playing, I couldn't stop talking about what a production version of this would look like. HABA would have a field day kitting this out with adorable wooden bits!
In reading your incredibly clear rules, we weren't sure if there was much to this. But, hoo boy, we were wrong. This little game is surprisingly tactical! We won, but on literally the last action of the game. And after a team discussion of how to proceed with the final round.
The amount of components is a big ask for a print-and-play and it makes the game a little fiddly. We wondered if the board was made of randomly organized tiles and you only have to place cubes on space marked with hippo colors. The special ability cubes could be printed on the tiles themselves. It's a possibility.
But if folks have enough bits to scatter on the table, it's pretty rewarding. Each color cube having a specific rule is great. One addition to your next draft would be a clear player aid to lay out what each color does.
It also forces team collaboration. As with any co-op, quarterbacking will no doubt happen with this, but that's on them, not you as a designer.
Our big question as a two-player team: must you always play with all four hippos? We did and it wasn't too difficult to keep focused, but I feel like your next edit (because this is so solid) could acknowledge scaling. It's my biggest fear and has me in cold sweats during design so I wish you luck there.
All in all, we thought this was super cute, surprisingly complex, and kind of a winner.
Cheers!