Hi there! Cute game, my daughter love Bubble Bobble and enjoyed this a lot too. Sadly couldn't get the controller version to work (might be my cheap controllers, they certainly don't work in every game! :-D) but managed to play the keyboard version fine.
A couple of thoughts:
Since the game is going to appeal to young children, being able to play with extra lives (or credits like the old Bubble Bobble) would be good.
It could do with the player being given a few seconds invulnerability when they respawn - a few times I respawned with an enemy basically already on top of my and instantly died.
I like the ability to drop down levels - gives the game its own identity and playing style a bit more.
Didn't quite reach level 20 but all in all this is a really promising start and I think younger players in particular will enjoy it. The trick will be of course adding extra variety through the hundred planned levels (which, FWIW, is something I felt the original Bubble Bobble failed to do well enough.)
Happy developing!!