I have personally taken the Lamainai tour with Tanashi and without hesitation would recommend it. US$125 if I remember correctly. While it is a 7A to 7P, lunch and light snacks are included, and you will have plenty of Belikin for the return leg;-}
Try the Winnie Estelle for a slow cruise to 2 or 3 snorkel spots and 2-3 hours on Caye Caulker. Some people want more privacy, as the Winnie is an old trawler that comfortably carries maybe 2 dozen people, but I liked the mingling. If your group was large enough a smaller boat could be comparably priced. Snacks, and adult beverages are free on the boat, as is snorkle equip.
Take your honey above the cut by cart or bike, or better still water taxi, to Caoricorn for lunch or dinner. A little spendy, but still a good value. If you're on a budget go to The Palapa about 1 mile North of the cut.