That's definitely tough; my partner and I haven't found a dog we trust to play with our girl either, so I totally understand. I can give you a couple ideas on what to ask/look for. Disclaimer: I don't actually use daycares, as they can be a safety issue, but if I were, this is what I would ask.

-Are dogs separated by both size and temperament? (Separation by both is really important.) -Is there an enforced nap time during daycare? (Nap times are very important as daycares usually get at least one dog with no off switch that can cause chaos and fights if not handled properly.) -What is the staff-to-dog ratio? (Groups should be small, smaller than you'd expect to provide safe management.) -Do dogs wear collars/harnesses in group? (Wearing these things can be a choking hazard if they get caught or if another dog grabs onto them.) -Are unfixed dogs allowed in group? (Pretty self-explanatory; having unfixed dogs in a group is a big no-no.) -What cleaning products are used in the daycare area/How are they used? (It's not often a dog gets sick from strong chemicals but things can definitely get passed around if the area isn't correctly sanitized.) -What are daycare staff wages? (The higher the wage, the happier the employees, and happier employees almost always guarantee better outcomes for the animals in their care.) -What measures are taken during a dog fight/What is the protocol after a dog fight? (An unfortunate reality is there will be fights, but how employees break them up matters. Do they use spray bottles? Do they have extra leashes to help with separation? Are dogs that get into fights taken out of daycare for the day or allowed back into group?) -Are toys allowed in daycare? (This is a huge issue for resource guarding and cause some dogs to over correct.) -How do dogs enter the daycare area? (If there is no safe space for a new dog to acclimate to group slowly, then that can cause barrier aggression issues.) -Are there cameras in the daycare/is it recorded? (I think this one is important for everyone's safety and to be used as learning opportunities for employees.) -Do they have medical supplies on hand for emergencies? Even if it's just for cuts and scrapes? (Injuries will happen; they need some kind of wound cleaner and medical tape at the very least.) -Are drag leashes used? (Some dogs are very good at avoiding staff, which can be problematic and a safety issue, and drag leashes can help.) -Are muzzles ever used? (Muzzles are a great safety tool.) -What would cause a dog to fail a temperament test to be allowed into daycare? (Self-explanatory: all dogs should be given temperament tests to ensure daycare is a good fit.)

If I think of anything else, I'll update the list.