Welcome to Cruise critic and the Princess forum.
Did you download the Princess Cruises App? You can select dining on there or there is a website version of the App on the website, under your cruise personalizer…
If you used a TA, they could help too.
If they like to eat early…go when the MDR opens on the first night and ask the host/hostess if they can get you a table every night at 5 pm, or whatever time they like. They are very helpful and may see another MDR that is available.
You cannot go a day early, they are not going to checkin for the sailing until the actual sailing date. You will go through a line to get inside, then follow tje blue line to pick up the medallion. All guests do have to checkin, show passports and required documents.
It usually goes pretty fast. We get to the port about 10-1030 and get inboard by 1100 or so.
If the older guests need a wheelchair, you can request one from an agent from Princess, they’ll bring it around for them to board.