...well that was weird. I'm beginning to think this Jan Wahl was an oddball.
Two FAT kids (fatness, food are a major theme) go on vacation with their parents to Atlantic City (back in the days of elderberry Kool Aid and sliced tongue), and are ill-tempered, bored, and reviled by the locals who hate summer visitors.
And they are tipped off to stay away from The Elephant Hotel. So naturally, they hatch a plan to find the abandoned place and break-in. And it's haunted. And it just gets weirder and weirder from this point on. Lots about gluttony (is it a cautionary tale?! I guess so? Fat, fatness, overeating and general food is central), and being haunted by a hungry ghost.
Ends in a clambake, following swimming lessons with their ghostly pal. It's bizarre, and it's free on OpenLibrary, and thank goodness for InternetArchive for preserving books like these! Not worth republishing, but certainly worth preserving a scan of it (illustrations in black and white are pretty amusing and detailed, especially the cross-section of the elephant-shaped hotel).