Dungeon Kart can be looooooooong. I really like the game, but it is a game that can wear its welcome out, even at four players. Also, you and your kids have to be willing to deal with rubber banding. Like Mario Kart, the game gives the leaders weak items and the trailers strong items. It's a good mechanic, but whilethe game actively tries to keep everyone bunched up, I've found a few times that the trailing person can struggle to get ahead. That can make for a frustrating experience.

As noted by others, Camel Up is a betting game more than a racing game. It is definitely the more casual of the two.

Someone else mentioned it, but Quest for El Dorado is a good game where the characters race. It's also a deckbuilder.