Fodor's Travel Talk Forums - Questions about Portugal

My family ( my husband and me and our three girls- now 9, 12, and 15) had planned a trip to Portugal for June 2020 which we had to cancel due to Covid. We have now rescheduled for this June 5-15 arriving the 6th. Having never been, we would love feedback on our itinerary and if we are trying to do too much or not enough...

Current plan
6/5 -6/6 Dulles-Lisbon arrive 10:40am: transfers from airport to Sintra
6/6-6/8- Stay at Sintra Boutique Hotel (see palaces, etc -assuming this is not enough time to see Cascais??)
6/8-6/12- Train (?) or car (??) to Lisbon to stay at Chiado Square Apartments- do all the fun Lisbon things
6/12-13- rent a car (or take a train??) and drive to Coimbra - stay at Solar Antigua Luxury Coimbra and check out local sights
6/13-15- train or drive (??) to Porto and stay at either Mercure Porto Centro Aliados, Apartamentos The Arc Carrís or Mo House.
6145- 12pm- fly from Porto to Dulles

My questions are....should we skip Coimbra and just fly or train straight from Lisbon to Porto and add a night in Porto? We love showing our three daughters different cities and have never been to Portugal ourselves. We love different restaurants and just enjoying good views while eating and having a glass of wine, seeing some top museums and other sights and generally enjoying the aura of a new city. I worry about cramming too much in...

Should we skip our quick stop in Coimbra to add a day in Porto or somewhere else? We also LOVE vineyards and while we don't know ourselves to be port wine fans, who knows until we try? Are there kid friendly ways to try port?

Humbly thankful for any advice!
Dabney