Mac King is really entertaining even though he isn't "new" but there were a ton of kids in the audience and they looked like they were having a lot of fun.
Also V The Ultimate Variety Show at the Aladdin is fun for kids too. There are people that juggle, jumping ropes, comedy, magic....kind of all in one. It's really good!
Not new either but some friends kids absolutely loved Ka and Mystere from Cirque.