Help! Risk Assessment for Farm Park trip

Hi all
Looking for some advice. We are planning to take the pre-school to the local farm park (typical one with indoor play centre too). Its only 10 mins by car and so the committee have decided that instead of hiring a coach etc then the parents will be responsible for transport there and back. The parents are organising it between themselves to transport each others children. Do we need a risk assessment for this and what do we include?
Once at the farm then either the parent stays with their child or the staff take over for those that are there without parents. We have asked the farm to provide us with their risks assessments what do we need to do ourselves?
Has anyone done a trip like this before? Any advice? Things we should consider?
Taking first aid, mobile, address book, register. accident forms etc.
Im new to this so trying to get as much info as I can! Thanks

[SomeoneSpecial]

you need letters to parents and the farm comfirming everything and make a list so you know how many kids your having in staff care. id do a risk assesment for the switch from a parent to staff and for the farm and then for arrangements getting back. but since the parents are meeting you there and are awear that they are responsible for their own children i do not think you need a risk assesment for that. but possibly for the whole group once at the farm.

hope this helps

[Kathie]

We are going to a similar place in Cornwall and parents will be responsible for own transport there and back and for their children. I haven't done risk assesment on this basis but have recieved Health and Saftey guidelines which i will photo copy and give to parents

Thanks for that. Will look into your points.