Your itinerary is totally feasible. You will be road be road weary, but it's do-able. With that being said, I will remind you of what Edward Abbey wrote in his classic
Desert Solitaire (a book that you should read before you get here), "A man on foot, on horseback or on a bicycle will see more, feel more, enjoy more in one mile than the motorized tourists can in a hundred miles." Having spent alot of time in the desert SW, I will agree with that statement 200%.
I agree with the comment on the needles district. To fully enjoy that section of the park, you really need a high clearance 4x4. The side trip to newspaper rock on UT211 is worth it tho. If you decide to go to Hovenweep (the same goes for valley of the gods), make sure the road is dry. It's very difficult to drive when wet, even in 4x4. FWIW, March and April are early season, and can be wet.
If you buy the national parks pass, it's also good for day use BLM (bureau of land management) pay sites. This includes Calf Creek Falls, and Road Canyon and Mule Canyon on Cedar Mesa (outside of Blanding and is highly recommended). It will not cover State Parks (goblin valley or dead horse point).
I would reccomend the desert rose inn in Bluff over anything in Mexican hat.
http://www.desertroseinn.com/ It's about 45-60 mins from (north) monument valley. I've stayed there and it's clean with wireless internet, etc. A little pricy (about $100 US), but there aren't many options in that part of the world. Personally, I'd avoid the hotels in Montecello and Blanding Ut. I've heard to many horror stories about them. Make sure you get something to eat before you get there if you are coming in late. There isn't a lot in this part of the world, and these little western towns shut down pretty early. Also, if you even THINK you are running short on petrol, fill her up.
Without the house tours, 1/2 a day in Mesa Verde is enough. Frankly, if you are willing to do a little walking, there are cooler, lesser know, places that will be closer to you. You already have the information in your hands, you just need to extract it. Remember what Abbey said and don't be afraid to get out of you car and do some walking. You wont regret it.