There seem to be some wonderful places to stop for lunch or overnight on the way to Porto. We will arrive in Lisbon late April 21 and then after a couple of days want to travel to Porto and then take the fast train to Lisbon so we can catch a plane out of Lisbon early May 2. Which stops/restaurants/hotels would you suggest during this two weeks.
Two places worth stopping at are Tomar and Coimbra although there are many more. Where to stop depends on what you want/like to see and do, and whether it’s a lunch stop or overnight. It would be a shame to drive from Lisbon to Porto and only stop someplace for lunch.
"two weeks" is being generous, you really have 9 full days, if you consider May 1st, you will be traveling back to Lisbon, packing, and getting ready to fly out.
If you spend 2 of those days in Lisbon (plus some bonus time on return May 1), and plan at least two full days in Porto, then you are down to 5 days.
Tomar and Coimbra would be high on my list as well. You could stop in Obidos on the way to Tomar. A neat town, worth a few hours walking around, but not much more. Near Coimbra are the Roman ruins of Conimbriga, well worth it since you will have a car. Your last day with the car, on the way to Porto, you could swing up through and drive down the Douro Valley,