OP, I'd forget this idea.
I was briefly a member of one of Cupcake when I lived in London and DS1 was a baby. It was a complete waste of money. I only joined because I didn't know anyone else with young children when I was pregnant and I had visions of spending my maternity leave entirely on my own.
It's a lovely idea and all very nicely presented but, in reality, it offers very little that you can't get elsewhere for a fraction of the cost, and a lot of the facilities seemed to be very lightly used. Some of the classes were popular, and the cafe was lovely, but there were very few play facilities (outside the creche) so once your baby was mobile, it had limited use.
It did occur to me that there might be scope for a less exclusive set-up which catered for children up to school age - a bigger cafe with carefully thought-out seating arrangements, and a small soft play, alongside studio space for classes and some other facilities. I got as far as looking into the costs (outside London but in an affluent area with lots of young families) and drawing up a very basic business plan.
It wouldn't work. The costs just don't work out for something of that nature. You'd either have to go small, very exclusive and eye-wateringly expensive, or big and considerably less expensive, which would mean that you couldn't offer the vast majority of facilities and would effectively just finish up with a very expensive soft play.
I looked at some other ideas, including a cafe/play/creche set up with a quiet area for parents to work, or just a large cafe with a small soft play and some group sessions and parent 'networking' facilities.
None of them added up. I still think there's scope for some well-planned facility for parents of small children, but you'd have to have some decent start-up cash, be extremely sure of your market, and be lucky enough to find affordable premises in a target-market area.