Never again - Ever
The Tourmobile should be called the Waitmobile. I understand traffic is congested in DC and there are a lot of people using the tour systems during Spring Break. The issue I had was the lack of Tourmobiles. The buses were sparse and did not arrive to pick us up at all of the stops for an excess of 45 minutes EVERY TIME, even though we were told they show up every 20 minutes. The wait at the Korean War Memorial was over an hour. Meanwhile, those of us waiting for Tourmobile watched the other two tour companies (whose stops were immediately adjacent to ours) shuttle in and out three times each. I won't name them, but one had two levels on their buses and the other had orange and green colors in their circular logo. We literally watched three two level buses and three orange and green shuttles pick up their customers while we waited for one of the Tourmobile buses.
Halfway through the day, we would wait for 30 minutes for a bus to arrive, and then call the number listed at the Tourmobile stops. Each time we called, and we were not the only families calling, we were met with indifference and were told a bus would "be there shortly." Zero customer service and horribly unapologetic employees. DO NOT use Tourmobile. If you use them and find the same horrible experience we did, don't say I didn't warn you. Do not be fooled by the "Authorized by the National Park Service," as I am sure that simply means they have a permit.
Another warning: The limited number of buses equalled full buses. While waiting at one of the stop points, if nobody gets off a bus and it is already full, you will have to wait another 45 minutes for another bus to pick you up. Hopefully, the next bus will not be full, or you will be waiting again.
One last thing, the seats inside the buses are extremely limited for leg room. I only stand 6' tall, and I had to sit with one leg in the aisle and the other turned sideways to fit.