Can't add them, only make a new ressie if there is availability. the only one you will have a problem with besides buffets will be LeCellier, if that's on your list. I just finished making my late April/early May ADRs and while I had no problem making ADRs for 2, on our second week when we have a larger group (only 6), it took 3 different days before the CM could find a time to accommodate a party of 6, unless you want 4:00PM or after 8:30PM, so you need to get on the phone soon. As the other poster said, they have to make new ADRs for the new party, then cancel your old ones.