If nobody here has one. Overtons.com has a nice selection. Keep in mind that some need 2 people in them to balance out. Inline ones can be solo or double. There is always the Manta Ray one. Kids will love it!
Don’t know how old your kids are but I have teens and we just bought a Big Mable. It holds two riders and has two different towable positions either sitting or kneeling. The sitting one was very stable.