My wife and I (mid-50's) had our youngest daughter and her husband (both late 20's) join us this year on a 7-day Quetico trip.  They did just fine, but I have to admit an inward smile or two as they struggled with wind and/or portages.  One portage, was particularly long and steep - son-in-law and I portaged the canoes across and as he was putting his canoe down, he said, 'that's the hardest thing I've ever done.'  I replied, 'great, now let's go get the packs'........ ;)