If were going in a group and a few people are 18+ but they dont need to drink can they get in?

It's a bar. They will ask for an ID.. Daytime is different though. Perhaps daytime is better for under age.

It's easier if you reserve a table. I walked in with my 4 year old nephew before 6:30pm. After 6:30pm no minors are allowed. (Under 18)

Nop

They ID at the bottom floor, most likely they can not enter.