Those banana boats are a favourite with my kids too. For an adult version some orange liqueur is a nice addition ! ... and a bit more liqueur while you wait for them to cook is good too.
Cored apples stuffed with dried fruits, chocolate, etc and some juice (or splash or water) (or some more of that liqueur) wrapped if foil in the coals is good too.
I'll be away with the gang in a couple of weeks so this has got me thinking that I'd like to bring along something new to try. I'll keep an eye out for some inspiration !
Keep 'em coming ....