Lagunamar is definitely an excellent choice. We are returning there a week from today for 13 nights in a 1BR. We have been twice before. YOu don't need to be on guard in the resort. There are no vendors in there pushing you to buy stuff. Though sometimes the spa people come around to try to get you to get free foot massage in hopes you sign up for spa services. There are vendors that walk the beach with all kinds of different items. But you don't need to be on guard.
One thing that first timers don't usually expect at shops and such in Cancun, which is different from other Caribbean islands, is that the vendors can be a little pushy. You will walk by a whole row of shops and every shop owner will motion for you and ask you to "come in to my store". We have seen this in every area we have traveled in Mexico, but we haven't noticed it in other areas of the Caribbean. It isn't bad, but can put some people off.
There is so much to see and do in the Yucatan. Snorkeling, great beaches, swimming, cenotes, Mayan Ruins. There is so much to see and do that I don't think you could ever run out of new things to do. Trips to Isla Mujeres, Puerto Morelos, Tulum, Playa del Carmen. Take the ferry to Isla Mujeres and rent a golf cart and tour the island. It will be a highlight of your trip.
The buses that run through the Hotel Zone are cheap, fast and only a few minutes apart. So getting anywhere in the hotel zone is easy and cheap. You can also take the bus to the ADO Bus station in downtown and go just about anywhere. Tours and activities are also plentiful and reasonably priced. I have found though that taxis in the hotel zone are not real cheap. At least my definition of cheap.
One of the most important things to do is to prebook your airport transportation to the resort. Do not show up without prearranged transportation or you will be eaten alive. There are so many in the "shark tank" at the airport that will offer you transportation for taking a timeshare tour. Don't do it. Prebook something through USA or Canada Transfers and then walk straight outside and find them with their sign. Real simple, but don't talk to anyone on the airport except at the immigration and customs area. Once past customs, head straight outside for your transfer. It can be a little bit of a shock when you first walk out with all the people there waiting for people with transfers, but just find the people for yours, and you are good to go.