I used to go to Akumal a lot when I worked for a rental company that represented most of the local condos and villas. It's been 3 years since Ive been there, so a lot may have changed. However, here are some tips that I hope make your vacation more enjoyable.
Casa Alux is a really nice house and you will really enjoy it. It's isn't beachfront (it's on the rocks) but almost all the villas in Akumal are like that. It's really close to Akumal Bay and the town. Akumal will be a nice change of pace over staying at an all-inclusive.
Definitely rent a car at the airport. You can use a golf cart in Akumal, but I've always rented a car instead. Don't ask for a newer car when renting and they probably won't hassle you over scratches and dings when you turn it in. Just make sure they mark everything in the rental agreement before you drive off the lot. Easy Way is cheap.
Cancun Car Rental, Rent a car in Cancun, Playa del Carmen Easy Way Car Rental Don't take your eyes off the pump when filling the vehicle at any of the gas stations.
There are two small grocery stores at the entrance to Akumal that will have pretty much everything you'll need for cooking at the house, as well as beer, liquor, beach stuff and gifts. There's also a breakfast counter called the "Akumal Luncheria" (or something like that) located just outside the main entrance to town. The omelettes are very good. This place is not for the faint of heart, but if you want to converse with the locals check it out. Watch out for the flies!
Lol Ha is hands down the one place you have to go for dinner. It is located on Akumal Bay. The wait staff and food are VERY good. La Buena Vida on Half Moon Bay is also top notch for dinner in the upstairs restaurant. Have lunch or afternoon drinks at one of their beachside tables. Their bar has the best nightlife in Akumal which isn't saying much. La Cueva Del Pescador (The Fish Curve?) located in the middle of town is also very popular, but I didn't care for the sand floor, mosquitos and over salted food. The Turtle Bay Bakery serves home cooked pastries for breakfast and sandwiches for lunch - very tasty. La Lunita on Half Moon Bay would be a third or fourth choice for dinner. Que Onda (near Yalku Lagoon) is a good Italian place with a unique ambience. Bring your bug spray.
The Akumal Dive Shop is the town's first dive operation. Akumal Dive Adventures is the other most chosen dive shop. The experience you will have at either one probably most depends on what DM you end up with. They are both established shops. driftwood is right on the money about Half Moon Bay - I remember years ago there was a big stink in town when The Akumal Dive Center opened. There supposedly had been a long standing agreement between everyone in Akumal that motorboats in Half Moon Bay were prohibited. I also heard about some local "tax" or "Akumal Association" fee that all the property owners paid to keep the town nice, that is except for the owner of this establishment. Again, I have no direct knowledge of this, only talk. Many would say the diving in this area is inferior to Cozumel. There are however many good spots if you get with the right crew. For Cenote diving Dos Ojos and Chac Mool are popular.
Akumal Tips
Make sure you check out Yalku Lagoon. This is a great snorkeling spot for beginners to advanced. Easy entry, 5-25 foot depth with some good swim throughs if you please. The water is brackish so there's no coral but there are often a ton of fish here.
The town is really small - basically one main road - two bays. You can't get lost. Akumal Bay (closer to the entry road) is good for swimming and walking the beach. Half Moon Bay is really pretty but not great for swimming.
Of course there are gift shops and vendors in town. Some of the local artists are amazing, especially Jose P. He carves some exquisite Mayan limestone pieces. He used to set up shop for the lunch crowd in Akumal, but the last time we saw him was on the Coba road, just past a town (sorry I can't remember the name) that's about halfway there from Tulum. His house is on the right just past town and he sets out his creations for passers-by to stop and browse.
Bring your basketball shoes. The locals have a full court just outside the main entrance to Akumal. They will welcome some friendly competition.
Outside of Akumal you could go to Tulum which is about 30 minutes south. This is a "big" town with lots of shops, restaurants, and more than a few bars. Nice beach and ruins. Take a left off 307, and turn right on the beach road, drive around the massive potholes to find a desolate beach paradise. The Coba ruins are a good hour inland from Tulum. They have partially restored many of the buildings and were still allowing people to climb a "pyramid" Nohoch-Mul? the last time I was there. Bring your walking shoes. There are a few cenotes to stop by for a swim on the way back. If you're doing the Tulum or Coba ruins go early before the busloads from Cancun arrive.
Xcaret is cool if you like the Disney sort of thing. They have a Mayan Ball Game that's worth seeing at dusk. This is a fun place for kids and families.
The wife and I are doing just the opposite as you this year. We've always stayed in a condo or villa in Akumal when visiting the area, however this time we got a free time share from her parents so we're going to the Grand Mayan near Playa Del Carmen.
Good luck and enjoy your trip!