I just re-read your orignal post and realized I misunderstood it - I thought you would only get to do Stingray City with the tour company and the ship excursion included Coral Gardens and 7 mile beach, so my response probably didn't make much sense. (Ah - that's what I get for responding before my norning cup of coffee
Anyway, to answer this question. The timing of that excursion should be perfect. The Buccaneer catamaran is a great way to do Stingray City and the crew is super! I have used them before and will actually be enjoying the experience again on Feb. 14 when we are in Grand Cayman. I'll give a full report when I get back.
(BTW - I'm glad you found my input helpful in making your port plans).