Yes you can. You can't make them until 90 days before and you will probably have to do it by phone because you won't have a reservation number. The phone number is 001 407 939 3463.
Depending on time of year, how many in your group and where you want to eat ADR's are not always needed. OK if you know exactly where and when you want to eat you might as well make them but this will be our 1st trip planning meals months in advance. We usually either just turn up and wait for a table(never more than 20 mins or so) or call at guest services a few hours before we want to eat to reserve a table.
If we didn't have free DDP theres no way I would plan a meal more than 2-3 hours before we ate, its going to be interesting having 16 meals planned.