None of the shows in Las Vegas have dress codes. You'll see people there in shorts and t shirts, jeans, maybe a few suits (rarely), and everything in between.
Personally I throw on a pair of Dockers or other slacks and a shirt with a collar and I leave the tennis shoes back at the hotel in favor of "real" shoes. That works for probably 90% of the restaurants in Las Vegas, and it works for 100% of the shows.

The VIP seat thing is not that big of a factor. Almost every show has them in some form, they might come with some gimmick like a free program or a "meet and greet" or something, but they're not going to have you stand up to be introduced or anything.