We booked the tour through Tripadvisor, so we were able to use a mobile ticket on our phone, which was nice.
We booked our tour for July 6, as the previous days were sold out. There was a severe thunderstorm going on as the tour was about to start, but they still showed up. The carts are equipped with clear plastic "walls" that can be unrolled and unzipped, so you stay dry. We had the three of us and a family of four on the cart.
The other dad and I are about 6'5", and we fit in the cart just fine. It was a little tough getting my legs out, but I also have bad knees, so it might be different for you.
Our tour guide, Shaina, assured us that we would unzip and roll the walls up if at all possible. She also had free ponchos if we wanted to use them; our teenager took advantage of that. The walls were rolled up at our first stop, and we left them up the rest of the two hours.
Shaina was AMAZING. She kept the information coming with a great sense of humor, and joked around with the kids. She offered up all kinds of little tidbits that you're not going to find on Wikipedia.
As for the stops:
-Stopped for a few minutes at the Capitol. Long enough to grab a few pictures, but you don't have time to walk up to it. (Do the Capitol Tour; it's worth it!)
-Stopped at MLK Memorial for about 10 minutes. There was a bathroom right next to the parking spot; this was about an hour into the two-hour tour, so the timing was perfect.
-Stopped at Lincoln Memorial for about 25 minutes. The roads were still closed off from the "A Capitol Fourth", so we had to hoof it up the sidewalk, instead of being dropped off closer.
-Stopped by the White House for a few minutes.
When the tour was over, Shaina offered to take us back to our starting point, but she also gave us the option to say "good night" and walk up to the White House. Since it was already 10 pm, we opted to go back to the station.
They tell you to meet at the Smithsonian Metro stop, which is partially true. Take the Independence Avenue Exit from the station, then turn right. The cars pull up at the corner of Independence and 12th, right by the steps of the Dept. of Agriculture building.
Cannot recommend this tour highly enough. There were plenty of "big bus" tours that we passed up, but this did not feel "cookie cutter" at all. I'd give Shaina 5 stars from each of us, but the website doesn't allow that.