We have a detailed Health & Safety policy document at the livery yard which everyone has to read and sign. I have had to sign on behalf of the grandchildren, and they are not allowed to be unsupervised anywhere until they are 13. We have large notices warning people that 'This is a working farm' and to take care. We all know who are the crabby-tempered animals and handle as appropriate. Luckily my two are sweethearts and follow 'to heel', can be tied up anywhere etc. One or two of the others are just a tad less trustworthy! We have a stallion on the yard who is extremely well-behaved but obviously you don't tie the other horses up nearby.