If you don't plan to fence it in then I would imagine you would give some prospective parents a reason not to bring their children to you for daycare. As for whether it is the front or back, even if the parents are responsible for their child out front, the liability is still possibly going to fall upon you and if an accident occurs the parents could sue. If I was in your position, I would have probably looked into regulations and any prospective safety issue before purchasing. Planning should really be done in advance and as I said, if you aren't planning on fencing it in, then in my opinion the risks outweigh the pros of having a pond with multiple children onsite....I'd be getting a refund.