I just do not want to plan to do a dive with someone who will be disappointed by the bottom time my 72's allow me.
I don't think its a real problem. Just be honest about your experience level. I dive with less experienced buddies at quarries quite a bit just to pass on what more experienced divers did for me when I was coming up the ranks. I will usually try to help them with their weighting, buyoancy, trim, etc. if they are amenable to that. I'm never disappointed when my less experienced buddy turns on gas. I'm usually just there to pass time, work on some skill, etc. Furthermore, 30 minutes is about all I can stand at the quarry before I start getting cold or bored unless I am really working on something, in which case I would not have agreed to dive with them.