I've never traveled with 9, but I have with 7.
We even got an ADR the day before on New Year's Day...I think it was the only one left though.
Also, I got all my ADRs for 7 next week within the 90 day mark...and I'm still finding availability for my dates. Even with Summer crowds as opposed to Value early December crowds.
I don't think you'll have too much trouble, just decide what you want in advance and call or go online as soon as the ADRs open up.
Just like any other ADRs you might have to be flexible with times, but don't worry too much.
Also, keep in mind the ones that fill up quickly regardless, and try to get them first.