There's also more regulations involved if you have more than 5 children per class. There are also extra insurance if you let the children go outside.
When we started ours (in AG) we had a lot of paperwork to do at the local Gemeinde (your business plan should be a nice thick document

) and then we had a visit from the local building assoc. with a rep. from the fire department to make sure our space fit the criteria for hosting children. The guy from the local fire department then said that since we were on the first floor (and not the ground floor) this would require a visit from the Kantonal fire department! Luckily, we had a Swiss man with us and he chummed up to them and so they settled everything with a phone call instead of an official visit.
There's a lot to consider.