My suggestion:
If you want the TA to do it, have them put the requests directly on the reservation through CRO/WDTC. This must be done prior to 5 days before arrival as the reservation will be downloaded by the resort on day 5 and CRO can no longer change the reservation. You won't find many TA's who will willingly fax your requests in for you.
Then you can fax in the requests yourself directly as a backup.