IANAL, but the art style itself likely wouldn't be an issue, since it's drawing inspiration from Don Bluth/Old Disney/Generic Oldschool Hand-Animation and (hopefully) isn't copying character designs, animations, etc.

The UI is attractive, but we aren't really in a position to properly critique it. Do some early playtesting if you're concerned, give people a task or just ask them to play normally and see if they hit any pain points. Printing out screenshots and using them as paper prototypes to ask questions might also be useful.