My family and I are turning our barn into a haunted house this Halloween. What can we do to cover our rears if someone gets hurt? Will a posted sign help?

It is in your own best interest to call your insurance company and request a liability waiver. I would say this would go a long way in 'protecting your rear' should someone trip or fall, or generally have an injury on your property, within this venue you are putting together. I would say, rather be safe then sorry. You may ask your insurance company as well, if you should post signage regarding this

You may already have sufficient property liability insurance on hand, I would check.

Tick

Your title indicates you are thinking a waiver will be an option, it is not going to work with children. A child can not waive his rights nor can a parent waive the rights of a minor. Tickle suugest calling your insurance company and that is the best place to start. I doubt if your traditional home owners policy will cover this but short term insurance can be bought for the life of the venue. I used to build haunted houses for a service organization that charged admision. We were open for about 10 days and served 15,000 people, insurance cost us about $1000 in 1980