Sorry but Wario Ware can totally be played sitting down. Everyone plays the games a little differently.
As for "getting them off their butts", just realize that you are the parent that needs to set time limits for your children with anything involving TV time and video games.
Showing them "Wii Sports" boxing will only result in them getting off their butts for about 5-10 minutes. If they really want to sit while playing they'll just stop playing the games that require them to stand.
Just remember you need to step in a restrict use of whatever it is, kids need balance and your guidance to live a balanced life.