if repainting is not in the future,
start with the MILD approach with chemicals and elbow grease.
working your way up the ladder to the more aggressive.
PHOTOS could help give you more accurate information.
also, what is the base paint of the boat and what do you think
the kids sprayed on it ??
I would try some 400 grit wet/dry sandpaper first . . . .
then, if all the paint does happen to come off, buff it out.
some sign painters will use Easy Off oven cleaner to remove
freshly painted lettering from vehicles. Of course, you run
the inherent risk of ruining the base paint .......
a mild citrus based remover may be good for the first step.
read, understand and follow the manufacturer's instructions
on all products you may use.
come back and let us know what worked for you