I want to have naked cakes that party guests can decorate at each table. What do you suggest? Also want to keep it somewhat healthy.. any ideas??

Can't help you with the healthy part

As for ideas, you could place a frosted smooth white cake at each table and get one of those Wilton frosting bag stands for each table and put bags full of icing with different colors in each with a tip. You could also leave a few containers with sprinkles and pre-made royal or gumpaste flowers to add.

Or, it might be fun to make it a contest. Leave a picture of a decorated cake at each table and get them to compete to see who can get their cake closest to the photo.