National Parks Pass recommended
Syv gave you a good suggestion on the national parks. If you are going to go to more than 3-4 of these parks on your trip, you'd save money by getting a National Parks Pass here.
Great rates!! I would get it in writing that this covers ALL expenses so you don't get fooled by any additional must-haves when you go to pick up the car.
Hotel chains and reservations is a hot topic!
I'm a tight-wad. That's one reason why I usually camp. If I do stay in hotels, they are almost always the cheapest hotels I can find. I have stayed in many Motel 6's. I have never had a problem with them. They aren't fancy but they are clean, the TV works, the shower is hot, and they often have a pool. What more do you need? (If they had coffeemakers in the rooms instead of having to go to the lobby for your morning cuppa joe, they would be perfect, imho.) I think those negative reviewers are the type that want a champagne experience on a beer budget.
Now, I know some travelers here really need to have access to internet connections and other business-type services. If you need those, you won't find them at Motel 6.
I've stayed in nicer places. Usually when my former work would send me to conferences out of town. So I've stayed in premium hotels a lot so I can make the comparison from experience. Quite frankly, I'm never more comfortable in their beds, their pillows are never that much nicer, nor are their showers enough better, to pay those premium rates. The exception to this is if you're staying for awhile instead of just for a night. I mean, there's a time and place where a fancier, resort-style hotel is worth the money. If you're staying a weekend or more and will have time to make use of amenities. But, if it's just a place to get some shut-eye for the night, the inexpensive chains are just fine, imho.
I really enjoy searching out cute, little mom-and-pop types of hotels but, quite often, especially if I'm on a bit of a speed run, I don't have time for that.
The inexpensive chains I've stayed in the most and have always been satisified with are Motel 6, Days Inn, and Super 8. Just like anything, there might be some bad ones in those chains but I haven't found one yet myself.
As for reservations, if you think you are going to be stopping for the night in an area where rooms might be tough to get....like a touristy-area on the weekend, for example....you might want to get reservations. I will sometimes get a reservation, just in case, but keep close at hand the phone number and cancellation policies so, if my plans change, I can cancel and still get a full refund.
The only places where you might have to pay more than $100/night for a decent room are in the heart of major metro areas...usually the downtown core areas. And some remote tourist areas (the Grand Canyon, for example). The outskirts of cities, airport areas of cities, and most any other place along the way will plenty of good lodging in the $40-80/night range.
Never been charged extra for anything...
I've had 4 people in rooms at Motel 6 with no extra charge. And, yes, they were registered. Maybe not all of them do this?
And, well, I always pack my own shampoo anyway so I don't worry about using the hotel stuff. But I always use the hotel soap and I have never been charged extra at Motel 6 for their soap.
Odd.