I used to manage a place like this. Do not underestimate how difficult it is!
You need a lot of capital and amazingly patient, hard working and reliable staff - who can pretty much double up as creche staff- as any play cafe with a lot of children/infants/toddlers, invariably end up with little ones trying to scoot out the door, coming behind the counter etc etc. even if the paremts are trying their hardest it's always difficult to have everyone on a good day!
Us mums are a tough market to please as well, most of us are readily armed with a list of complaints - and why not want the best for our pride and joy?!
The cleaning and maintenance is paramount in these places, which I think is part of the reason why peole stop going to them. Everyone thinks the place is great when it's all shiny and new, but when the toddlers are unleashed on the place, it soons ends up like a slightly grubby house that doesn't feel much of a treat to escape to!
The rents are astronomical, but to be a success you need to be where the mums are, and that's always a pricey housing market. My advice would be to open a wonderful cafe that welcomes all, has high standards of cleanliness, interesting edibles that not everyone stocks, and make it child friendly - but not specifically aimed at this market. These places just get a battering that a cafe can't take - that's why play centres are still so popular, they are built to take a battering and are not very parent orientated. In my opinion it is v tricky to meld the two without a HUGE space. First and foremost where mums and small children are concerned, the key is great, friendly, caring staff.