I did a hiking tour of many of the trails with my mother two years ago (she was 76 at the time), and I assure you that the trails are really not going to be nice to your knees or hips if you don’t build up your endurance first! I have never used walking poles before, but for these hikes you definitely need them since there are many uneven “steps” as you go up and down different switchbacks. There are plenty of flat parts, but the trails do get crowded with people passing, and other large tour groups like ours. We had 30 in our group, but the largest tour we passed had 100. We were also there in early April BEFORE it got even busier.
I will say that I have never seen better scenery while hiking (including hiking the Alps in Switzerland), and not all the trails are the same, so do your research and pick the easier routes. Just be prepared with hiking poles, good hiking shoes that protect your ankles, and enjoy your trip! The towns themselves were ok, but with all the tour buses full of people (cruise ships also bring a lot daily) it felt overrun with people. The trails is where I felt I enjoyed the best part of Cinque Terra.
Our tour used Portovenere as the base, and it has a ferry that runs to the Cinque Terra towns. If the sea is too choppy though, it won’t run, but I felt there was more to do there at night. Plus the Fortress is fun to visit and there is a small island across the small bay that has a nice easier loop. Good Luck!