I love that you chosed to join with your 9y daughter .
So my biggest advice is to scope small like when the theme reveals think of an idea break it into a small pieces chose the best one that it would be good and would fit the theme then prototype it quickly if it was fun then build on it if it wasn't change the idea or change it so it so it can be fun. The scope part dont think you can do multiple bosses multiple areas multiple enemy types just dont plan huge try to minimize any thing you only have 7 days so make everything in the first 5 and polish in last 2 days btw any thing you want to make will take longer than you expect
2nd PLAYTEST PLAYTEST you are the dev you know everything like how to play it you will be pro in your game so you won't know if it was hard or not just give the game to anyone you know from your family, friends maybe your daughter that you will join with if it was hard for new players just tween the difficulty till it would be good if a level was normal for you it would be hard for us if a level was hard for you it would be impossible for us
Sorry if you didn't understand parts i just wake up so my brain isn't fully functioning well so just ask me if you got anything i joind around 8 jams so ig i have a good amount of knowledge to help you with