Hi
Picking a best date is a tough one, all the tours usually catch decent storms and every year is different. I'd say T4 is a bit different to the first three because it is usually up on the northern plains, which makes it more of a unique experience, but weather wise it's impossible to call.
We usually collect from the airport, though some guests like to fly in a day early to acclimatise before the tour starts and we'll let everyone know which hotel would be best (our usual Dallas start point, The Best Western in Irving is shut for refurbishment next year, so I'll have to do a bit of hunting around to confirm where we'll be.
Single travellers are very welcome, and we will always try to put like minded people together for room sharing, or there is the option to reserve a single room for a surcharge.
We tend to have less down time than some other tour companies as we know just how storm starved most Brits are, so we will chase anything that looks interesting rather than waiting for moderate risk days. When we do get a day or two to relax we try to visit interesting places, national parks or spend some time mooching around downtown in local cities, and we have had some competitive crazy golf tournaments in the past. In the evenings we've been known to bowl, or find a decent place to eat with added entertainment (like the Big Texan Steak Ranch - which might not be on your shortlist...)
We can't make guarantees about the weather, it does what it does, all we can do is try our hardest to make sure you get to see the best of what the weather has to offer.
Foodwise, most places on the road have vegetarian options, but it can be quite a restricted choice in 'mom & pop' diners. We've had vegetarians tour a few times and I don't think any wasted away while travelling but I'm not sure if we've had a vegan on tour before. You're right, Walmart is everywhere and you can stock up with snacks there for nibbling in the car.
Feel free to email via the contact options on the site if you have any other questions.
Ian