Flying out of Lisbon or Porto

I think you would actually see more by staying in Lisbon three days versus traveling, but I’d also compare the flights, as Lisbon may have fewer connections.

flying out of Porto which sound much easier than Lisbon

I flew out of Lisbon a couple of months ago and it was easy, uber is super cheap in Portugal so just uber from the hotel to the airport.

You only have 3 days and you want to go to 2 places, and you want to drive????

Plan 2 gives you no time in Porto, so why even bother to drive there?

Two days in Lisbon is barely any time at all either, especially with teenage kids who
may not be in synch with your plans.

Note that Lisbon is a fairly hilly city, so if you choose to walk around, be prepared for
some climbs, and the weather may be hot.

Thank you so much! Agree that we should either focus on Lisbon for 3 days or Porto. Given the age of our kids and first time to Portugal would you recommend Lisbon over Porto despite the crowd in June?

While I like both cities, if I was traveling with my kids when they were teenagers, I would pick Lisbon. There is much more to do.

Another vote for just Lisbon, and keeping logistics simple.

From a crowds perspective, Lisbon is a "real" city, so while there is definitely going to be crowding in the core/central part of the city - like the Praça do Comércio and the roads leading up from there (lined with restaurants and stores) & the elevator area (closed when we were there last month) as well as up to the cathedral area. But step a bit out of those area and the city opens up, and the things to see and do are spread across the city.

Of course, you'll want to reserve tickets for the places that need tickets and you want to see (nearby Jeronimos church and monastery is worth it), but that would also be true in Porto or anywhere else in the summer. For our trip last month, we included a "free" walking tour that was a couple hours long and well worth it (pay what you choose). Despite having been in Lisbon a few years ago, the walk provided more historic info and a chance to ask the guide many questions, and would likely be good for teens too.

On the "downside" of flying out of Lisbon, the airport is a bit of a mess with regards to the EES process. The 3 hours early maxim is currently true in full force. Not sure if the Porto option would still route you through Lisbon airport, would connect somewhere in the US instead, or would use a different EU airport to transfer, but those transfers would dictate when EES exit takes place and how much wiggle room you would want at the start or the transfer period.

First welcome to Portugal! Hope you and your family enjoy it here.

I’d go with option 1 (stay in Lisbon).
With only ~3 days, option 2 will feel rushed, you’ll lose a big chunk of your last day driving instead of enjoying places.
Lisbon + 1–2 easy day trips (Sintra, maybe Cascais) already gives you plenty of culture without crowds if you time it well.
Flying out of Porto might be slightly easier, but not enough to justify the extra moving around.
Short version: less travel, more enjoyment so stay in Lisbon!