At our local cricket club a lady has rented a small area put the back and put in soft play equipment outdoors but packed away in a shed overnight. Large soft blocks etc. She also has several sit and ride toys, tractors, cars etc for toddlers. She has rabbits as well. She charges £4 per session of 2 hours. DS he sells parents coffee/tea for £1.50 per cup and juice in a little cup for 30p or a jug for £1.50. she seems quite busy at weekends when I go to cricket with son and I know she is open 3 days a week 10-4 pm but not sure how busy weekdays. She has 2 fun days organised in July and August and is having face painting and balloon entertainer. I would say suitable for 1-3/4 years. I have no idea how much she rents area from cricket club for but could try to find out.

You are highly unlikely to get a grant, you will need a loan to fund it if you haven't got cash. Look up the BIPL and see if they are in your area for help and advice. They are usually based in libraries.
Some things to consider:
Renting or purchase of premises that have the necessary permission for use from the council.
Customer parking.
Staff, hiring, training, contracts.
Insurance.
Health and safety.
Advertising.
Pricing.
Food hygiene registration as well as certification.
Accounting.
Obviously the more of some of these things you can take care of yourself the cheaper it will be.