Perhaps 'Bone,' it's light-hearted though it is a little long and fantasy adventure, maybe 'boy-ish', it's pretty accessible though.
Also 'Laika' is the story of the first living thing sent into space, a lovable dog, it's sweet and melancholy, really beautiful to look at.
Chris Ware's 'Jimmy Corrigan' is another beautiful object though definitely not light-hearted, it's basically melancholy but pretty accessible to non-comics readers.
Aaaand... 'Kampung Boy' is an autobiographical account of growing up in the jungle of Malaysia, again a beautiful book, black and white, slice of life kind of stuff though it is part 1 of 2 and frankly part 2 isn't quite as interesting.
Damn, comics for Mom is a hard request!