Regarding the tan suits, you can rent from Jos A Banks. I believe it's called the Al Fresco, if I remember correctly. If you want light gray, you can rent from Mens Warehouse or Jos A Banks. Smaller tux shops may have tan suits as well.
Regarding the Welcome/Rehearsal Dinner, they are not letting us have it at an a la carte restaurant. They have offered that we can have it at the buffet or pay an additional fee per person for the Beach BBQ, but they will not allow it in one of the sit-down establishments. I was extremely disappointed by this. I refuse to pay one more penny to this resort for the Beach BBQ (and I do not have another $1500 in my budget at this point), so I guess I am stuck with the buffet, which was not my vision at all.