Starcross

Somebody's got to save the known Universe. Again.
Art Mumby, his mostly irritating younger sister, Myrtle, and their mother have been invited to take a vacation at Starcoss, the finest sea-bathing resort in the entire Asteriod Belt. Just one problem... there are no seas anywhere in the Asteroid Belt, and that's just the first sign that the hotel is not what it seems.
Sure enough, Art and family quickly find themselves face to face with French spies, Yankee rebels and man-eating starfish, not to mention an awful lot of sinister top hats. As they travel to the future and back to prehistoric Mars, it's all Art can do to keep his head about him. Which is all the more important considering everyone else is losing theirs.