If I look to your priorities, I must say it's perfect! 2.5 days in Lisbon and 2 days in Sintra is ok to know the major things in both places with no stress.
If you have the opportunity to deliver the car in Sintra,leaving Lisbon to the end, maybe you have some more time available for sightseeing.

I would suggest doing your sightseeing in Lisbon first - upon arrival - and rent the car when you're ready to leave. That will give you some time to get over jet lag (and rest up from your wedding!) before having to drive somewhere.

Wow, you sound like us as far as likes/dislikes! I am trying to plan our honeymoon too... was considering Italy, Croatia, Ireland, Greece.... now I'm considering Portugal too.

HOW WAS IT!?

We are planning for a Honeymoon too after our June wedding, however we only have a week and I am now bottled down to either Greece or Portugal..Your idea of Honeymoon sounds familiar to what we are looking for..beaches, relaxing, culture, food, wine...what would be a best itinerary for 8-day trip?? suggestions??

I'd start a new post, if you haven't already. I doubt the OP will come back and see this but if you start a new thread, you will get suggestions.

I an headed to Lisbon in late May - we will actually stay in a nearby sea town, Cascais. I think it will be a great mix of urban and sea. Quite a few daytrip possibilites for days you don't feel like chillin'. IMO the logistics of Portugal will be a bit easier to do a week trip to than Greece (well unless you are from Europe).

Thanks for your reply Suec1.

i am flying in from US and the whole visa thing is going to take longer than i thought..So we changed plans and looking for smwhere closer to the US..probably Caribbean.