The following are in PDC:
Scuba Diving Playa del Carmen | Pro PADI Dive Shop | Mexico Blue Dream Don't know anything first hand about them, but they do show a WhatsApp number at the top of the screen, so should be easy to contact for info
Snorkeling in PLAYA DEL CARMEN with Dressel Divers Only dove with them and thought they were good; can't vouch for snorkeling. The hype on the webpage may be better than the actual snorkeling. Contact is through their main offices in Spain (I believe.) I used a WhatsApp number to the Dressel PDC dive shop we dove with - maybe they can give you another number or contact of a Dressel closer to where you're staying so you can see what they might offer you. The number is/was +52 984 879 5026
Dive Company in Mexico & Dominican Republic | Pro Dive International Again, only dove with them and only in Cozumel, but they have locations in PDC and offer snorkeling
Akumal is the only place I've snorkeled (with the turtles) around PDC. Maybe some diving from there as others snorkel. Great beach!
It appears that all of ops above do separate dive/snorkel trips, but you never know until you ask. I would email or call (Mexico should be free) to see what they can offer you.
I would follow
@Streydog 's advice as the ops on Cozumel are more likely to offer snorkelers and divers going out at the same time. The last time I was in PDC, I did 2 dives in Cozumel that were set up by Dressel. The benefit to that was that they took us to the ferry, had a boat waiting for us that took us to the Dressel (at the Iberostar) in Coz, and that took us back to the ferry after the dives (as a bonus, it also included the buffet at the Iberostar.) The only thing it cut out was a long taxi ride to and from Dressel/Iberostar - maybe something to think about with 10 people.
Another possibility I'm aware of is at El Cid La Ceiba in Coz. There is an on-site dive op, Babieca - can't vouch for them as I dove with someone else when I stayed there - but there is a pretty nice snorkeling area - free snorkeling while 3 dive - also a beach area, but iron shore - there are steps to walk down to snorkel. Think they only do boat dives during the day (the only shore dive from them is at night.) A day pass might be required to snorkel, but maybe not if there are divers. I'm staying there again next Dec.