My Aunts are visiting from the States and they haven't been in London in 50 years. I'm struggling to think of things to take them to, seeing as we only have two full days with them and they have slightly limited mobility (as in, they can walk fine, but my usual tourist show-off jaunts entail at least a couple of miles walking throughout the day and I think that might be too much, and like most older people who live in America, they are slightly bemused and repulsed by our public transport). Please help?