We live here part time. Actually, right across from Sandals in Aldea Zama.
Kaan Luum Lagoon - it's like $200 Mx to enter
Mayan Ruins in Tulum - $200 Mx to enter for non local
Mayan Ruins: Coba / Chi Itz - I prefer driving vs a shuttle but there are several great tour operators.
Cenotes: the best aren't really in Tulum. You have dos ojos north, you have jardin del Eden in Xpu Ha, Zacil Ha outside of Tulum (not as crowded), Corazon del Paraiso, and if you go to Kaan Luum, theres a great spot right down the highway : Xa'ay Ha.
Which beach are you supposed to go to? We like Cinco (north) Coco Tulum (central) and Dos Ciebas (south). They have very reasonable prices for day passes. I'll ask my other half about some other recs too.
Food: Alfonsina, la pizzine in la veleta, tu Tulum, gloria de don Pepe, suko Thai, the dumpling place (I can't think of the name), Alma Verde, Burrito Amor, and the pizza place next to the market in aldea Zama right across from the hotel is really good too. Carusa also has amazing fried and baked empeñadas. Wang is the name of the amazing noodle / dumpling place.
If you don't want to drive around town for food use tomato.mx. It's the local version of Uber eats.
Edit to add the Sarg won't be bad until later in the summer. It's been pretty clear the last couple of months. It usually starts to pickup mid June but that's becoming earlier each year. Luckily we don't get it nearly as bad as PDC and Cancun.
You could do a sound healing / cacao ceremony. Those are super cool. Om Collective does sound healings on Wednesday nights. Holistika runs some pretty cool activities too.