We fished the lagoon side a few years back....its a hot way to catch small tarpon, snook, etc...so it was a meh, for me.
Blue water can be good. We have done that several times along Riviera Maya. Its a short boat trip and it seems you can always catch mahi and have your hotel/resort cook up for you. We have never not caught mahi.
For a group that size I'd probably check out Puerto Aventuras.