Not much use in England though.
The Unfair Contract Terms Act prevents organisers from excluding or restricting liability for injury or death caused as a result of their negligence.
“A person cannot by reference to any contract term or to a notice given to persons generally or to particular persons exclude or restrict his liability for death or personal injury resulting from negligence.”
But
almost certainly irrelevant in the OP's case, I think.
The OP does not seem to be proposing to charge the riders a fee. Or any of the conditions needed for an actionable contract to exist - offer, acceptance, consideration and intention to create legal relations. I can't see what consideration flows from the invited rider to the organiser - "if I turn up and take part in this ride you're leading then I'll....." what? Consideration must flow from the promisee, and all that.
English Contract Law, explained by our good friend Wikipedia. It's not really that complicated:
https://en.wikipedia.org/wiki/English_contract_law
I don't know too much about meet.com. I had a quick gander, and it seems they might charge a fee, but I can't really see that that changes much.
The OP may well have
tortious liabilities, but so have we all. Whether something happens, and the OP is found to have been negligent, in tort, and therefore damages are due, is another matter. Well, unless his lion escapes of course.