Hi! Happy Birthday in advance (I turned 40 last year, so I can relate
My Fiance and I stayed at Woody's (Corona Del Mar) last year, and found the staff (and prior guests that hung out there) very friendly! We plan on returning for some of our honeymoon this year...
As far as stuff away from Ambegris Caye (AC), I would recommend either a cave-tubing/zoo and/or Maya ruins day; we'd stayed in the jungle before AC and loved both.
I can recommend doing the snorkeling too; Belize water is warm, clear, and the fish life is abundant.
I don't have any particular operators to recommend for activities (I/we did diving vs. snorkeling, and the ruins/caves were all arranged by Jaguar Paw when we stayed there). However, this site and the boards are hopefully a good place to start... Good luck!