It wouldn't make a difference having too few. Just let them know when you get there. As long as you're not a party of 2 turning in to a party of 10 most places would be fine and having 1 or 2 less isn't an issue.
Earlier this month we had a late lunch ADR at Coral Reef for 4 people. My DD and her BFF decided to do AK instead that afternoon, so lunch at Coral Reef was down to just DS and me. I just told them when we checked in that only 2 of us would be dining and there wasn't a problem.
I think you would only have a problem if you showed up with more people that required a change in table size (e.g going from 4 to 5, while 3 to 4 is probably no big deal). Going down from 7 to 6 shouldn't be a problem. Remember that some places are charged in advance (like CRT), so you would need to cancel the extra person.