Please review this itinerary - thank you in advance!

Looks pretty good to me.

When renting a car make sure you pickup the electronic toll device. The highway you'd have to take going from Tomar to Castelo de Vide is electronic toll.

As for your questions:
1. I would not exchange Tomar for Coimbra. For starters, its out of the way, but also there is just no reason to. Its not actually in any way more beautiful than any of the other places. Do note that Coimbra is a full blown town, while Tomar is basically just the UNESCO enlisted convent.

1. I thought you were staying in Marvao? Also, where did you hear Marvao is stunning? I'm the only person on this forum who advocates travel to that part of Portugal :D Yes it is a stunning place, a small, fully walled town perched on top of a hill in Serra Mamede, you can check out some pictures on my site: http://www.aroundtheworld.org/portugal/marvao-serra-mamede (also pictures of other places on your itinerary).

2. Not really (other than Castelo de Vide you mentioned). But there are places between Lisbon and Tomar - Obidos, Batalha, Alcobaca, Fatima. How much time you want to allocate to that is up to you. It takes about 3 hours to drive from Lisbon to Tomar to Marvao.

3. I have never found central Alentejo interesting. The interesting towns are closer to the border with Spain - Monsaraz, Mourao, Moura, Serpa, Mertola. I did not find Beja interesting, I was there last year.

Thank you so much for your thorough response! I heard about Marvao, I think, on a random viewing of a Fodor's forum perhaps? or else on Trip Advisor. Loved your photos! Absolutely gorgeous. I'm still considering possibly Batalha instead of Tomar - any opinions on that? I feel like if we see the monastery at Belem maybe we don't really need to see the ones at Alcobaca and Batalha.

Thanks again!!

Nothing is really quite like Belem - the Monasterio de Jeronimos and Torre de Belem are one of the more impressive sights in Portugal, and is the best example of Manueline style. Batalha is more strictly Gothic. I would say that Tomar has more Manueline elements than Batalha, but Tomar has the round church with the octagonal altar, as well as its kind of merged with the castle, making it in my opinion, more interesting.

Of the three, Alcobaca is the one that looks more, well, "bare". BUT its the largest (highest?) church in Portugal and deservedly impressive due to the sheer size.

You may want to know that most people with their own wheels visit all three in one day. There is also a discounted single ticket for all three monuments as long as you visit all three in one day. Whether or not this makes sense depends on how fast you can get out of Lisbon that morning, and at what time you'd like to arrive in Marvao.

Thank you mredman - that was exactly the kind of comparison I needed! I think for now we will just do Tomar as I'm not sure how quickly we will get out of Lisbon - we pick up the car that morning and rental offices can be busy sometimes.

Thank you again for reassuring me about my itinerary! You really helped....

Mary

You're welcome, have a good trip