As Yulilin3 posted, there are
ECV/WC accessible tables, but it's not that the tables are different from the other tables, it's that they locate them so that there is at least one unobstructed side and are easily accessed by
ECVs and WCs.
Another thing is if you don't think he'll need the chair for the party but are bringing it just in case, there are loaner wheelchairs for the party.
The advertised start time is 7:00, however there is a "Surprise & Delight" and so the party actually starts at 6:45. Guests can check in and get their credentials much earlier than 6:45 if they wish just to get it out of the way, but there is no advantage. If you want to maximum your party time, I would check in between 6:35 and 6:45.
I've messaged you with a few questions.