We are going to be in DC for a few days next week with a 7 year old and a 4 year old. My four year old is averse to walking long distances and I am thinking it will probably be pretty hot in DC in mid-July. I want the kids to see the monuments but I think walking around to see them will be too much of a trek. Has anyone done one of the hop on/hop off tour busses/trolleys? Are they worth it? Is there a company you'd recommend over others? There seem to be a few different ones. Thanks!