Pompeii

It is possible but you might want to reconsider. It is a massive area with a lot of walking on very uneven surfaces. Go to a Goggle map of Pompeii to see the terrain. It is up and down and you can go slow but it very exposed with min shade. As I remember the bus parking lot is a the low end so it is mostly uphill from there. I don't remember a lot of benches to rest on. They might be there but I just didn't notice them.

As a substitute you might consider Ostia Antica just outside of Rome. It is flat, shaded, and much smaller. Similar buried towns but not a completely equal comparison.

Check out the website which has the Google view the previous poster mentioned: http://www.pompeiisites.org/index.jsp?idProgetto=2

It really is worth visiting even if you just see the highlights.

If you're like us and will be on a set tour, you may be stuck, unless the tour group can help out. Most times the tour leader will be able to suggest something.

If not, I've read about, but never been to, Herculaneum (the other city buried in the eruption) as an excellent alternative. It is supposed to be smaller, much less touristy and crowded, and easier to get around. IIRC it has a stop on the Circumvesuviano rail line too. Here's the link to Rick on them both: http://www.ricksteves.com/europe/italy/pompeii-herculaneum

Ercolano is a good alternative, some sloping streets but smaller than Pompei and more level.

I would also recommend Ostia Antica, if that's an option for you. There's a common misconception that it's much smaller than Pompeii, but the reality is that the site itself is actually bigger: New finds show Ostia is bigger than Pompeii.

That said, the part of Ostia that is open to tourists is indeed somewhat smaller than Pompeii, but not by that much. As pointed out, it's much easier to get around in than Pompeii. Ostia Antica is also easier to see because the bulk of it runs along the axis of the main street, unlike Pompeii which sprawls all over the place. And there are lots of places to sit, including the ancient public toilets. :-)

IMHO Ercolano is not a good substitute in your case because it's in a pit that you only get to by going down a long, long ramp, which is also the only way out.

Less crowding at Ostia Antica would make it easier to go at your own pace. Rick has a downloadable Audio Tour available, in the Rome section. Don't count on many official benches, but you can often sit on ruins themselves, especially in the theater; there is also a cafeteria at the entrance.

Laura, the cafeteria at Ostia is not at the entrance. It's in the middle of the ruins, past the amphitheatre.

In your situation, I would consider a private tour of Pompeii so the tour guide can tailor it to your needs and if you need to sit down, he or she will be able to accommodate you however on a group tour, the guide has to keep the group moving. Perhaps you've already thought of this, but I would take one of those little folding seats so that you can sit when necessary (at Pompeii or anywhere else during your trip). When I visited Italy in 2009 I had a foot problem and took one of those tripod-seats (purchased from REI) for the purpose of sitting when I needed to. You can also purchase a cane that folds out into a little chair. There weren't benches in Pompeii but if you take a little fold-out seat and if you take a private tour, then you can stop as you need to. We had an excellent private tour guide for Pompeii and Herculaneum this past September and he was really good about positioning us in the shade wherever possible as it was a very hot day. He was also thoughtful about stopping for water breaks, etc. and in your case, a private guide would be sensitive to whether you needed to stop and rest for a while whereas on a group tour, you don't have that flexibility.