Sorry for the long delay in responding, but I must have missed your request when you first posted it. I can't name anyone specifically, but there are several bird guides based at Tikal. The problem might be if they are booked up before you get there. I have a phone number on my web-page for Tikal (see link below), but its quite a few years since I last went there and it may no longer be working. Cerro Cahui is worth visiting if you are in Flores.
Good luck with it.