I would want separate sleeping areas as most dogs won't want to be sleeping with other strange dogs.
I would also want 24 hour supervision especially if they are interacting with dogs I don't know. I work in an emergency vet and we are often getting dogs in that have been fighting when chucked together by dog walkers etc, even the nicest dogs can bite when in a stressful environment they aren't used too with strange dogs. Add in toys and treats and it does have potential to be a disaster.
Op have you considered going on a course about basic dog behaviour? It's difficult as lots of behaviourists don't agree with slots of strange dogs in groups as it's often very stressful for them despite what people think. The vast majority of dogs show stress behaviour when you watch footage of some daycare type things.
I would want each dog individually assessed if it was going to go in a group with other dogs and removed at the first sign of it being uncomfortable (which is at the point most people can't read stress signals!)
If it were me I would have large kennels and maybe swap the amount of time the dogs are out, allowing only a few to interact with eachother at a time but with space to go and sleep afterwards. Most dogs play in twos anyway and if you watch dogs playing it's generally two wresting with others standing on the sidelines not doing much 
The day care near me does this and as far as I know it works well. Each dog has a large run with a bed/kennel area at the end so space to get away from others but they have a few communal areas where the dogs can get out and play. The runs are surrounding areas where people are (around the outside of the indoor play area) so the dogs aren't alone as such but are safe and not unsupervised and can watch what's going on and not get bored.
Unfortunately working with other people's dogs often means working with spoilt badly trained pets that owners don't see any issue with so that's something to be aware of, chances are the dogs won't all be as lovely as you hope!
I expect you would also need basic first aid and the ability to work from very early in the morning to very late and night.
Good luck I hope it goes well.