It would be better from a liability standpoint to post signs warning about being careful on the property as opposed to signs not being responsible for accidents on site. The rationale is that under the law, if one has a dangerous condition on his or her property, the property owner could very well be responsible for injuries sustained by a third person given the circumstances leading to any mishap.I also suggest that you have adequate liability insurance in place during the estate auction of your late father on the parcel where the event is happening.