Hope you get rid of those crashes, that's no good!
Before you go too far down the very low-resolution pixel art, take a look at some of the later CAVE shmups, they are a happy medium in my eyes.
Skip ahead to around minute 9:00 to see some of the more modern shmups, they look glorious.
Good luck with the project, that is so cute and nice to have your daughter work on the art, I am always trying to get my older son to help me out also, still looking for an in, he might help me with story and dialogue, he's a great writer and for video game dialogue, being used to being limited to 140 characters or less per line is actually a plus!