Similar to what others were saying in that other post.... Still think of it as a solo trip. Your not vacationing together your vacationing at the same time. Present it that way and expectations will be set. I use to have similar problems when I backpacked. Friends always bailed out at the last minute or keeping me "off schedule". I eventually learned to treat each trip as a solo trip, asking friends who wanted to joing to do so. I would let them know the route and the pace I was going to keep. If they wanted to spend hours taking pictures and lunching at scenic overlooks then I'll meet up with them along the trail at some point.
