Waivers are not worth much, but real informed consent and professionalism usually are. Start with issues of safety and how to act around bees and be thorough. That should include training on bee stings and the issues related to that. No one should be close to the apiary until they get a safety briefing or training. Then they can sign a waiver, or some sort of statement saying both that they understand the risks and they agree to follow the rules or guidelines that the club sets up for the apiary. Give them a certificate that says they have completed a one hour course in basic bee safety.
In the safety training, you might ask the group if anyone is allergic to bee stings. A high percent of the general population will say they are, that they got stung once and it was red and swollen for a whole day. Explain that is not an allergy - it is the normal inflammation that occurs in many people.
Explain that a real allergy involves life threatening responses, like the air ways swelling up to the point that one cannot breath. Explain that sometimes people get allergies without knowing about it, it is just a fact of the world. Explain that people that know that they have a true allergy to bee stings are putting their life at risk to be out working with a hive. Explain what an Epi-pen is and how it will be used if someone experiences a severe reaction.
Then give people the opportunity to back out if this new understanding of the reality of the world makes them feel uneasy (with an offer to fully refund the course fee or membership if one was charged). Make it clear that there is no pressure, that there is only an opportunity for those that understand the risks and make an informed decision of their own.
One of the rules that a club might benefit from is that beginners are not allowed to be anywhere near the hive alone. If they drop a frame and panic or get stung and go into anaphylactic shock, there will be trouble. If they just want to observe the hive and see how close they can get without protection, there could be trouble. If there is an experienced beek on hand that has the experience or training, most situations can be dealt with. Age limits and parental signatures for minors are also important.
Don't meet right by the hive. Start a meeting at a spot in the parking lot or extension building. Before going to the hive, talk about what is going to be done, who is going to wear what protective equipment, how the weather and other conditions might be affecting the bees, etc. Ask how everyone is feeling today - both as small talk, and as a way to identify who might be feeling bad or otherwise is not 100%. Have some Q and A to get people working as a team. Then walk to the hive.
If a club is mindful of the risks and acts responsibly, those actions will go a long to convince a jury that there was no negligence ... that any incident was unfortunate but was not the fault of the club.