My daughter will be going to London late March for a wedding. I will be joining her from the southeast USA so we can travel afterwards for a week together to Portugal, mainly Lisbon and Porto. I'm thinking it best to meet her at Heathrow since she'll already be there and then take an TAP or British Airways flight together to either Lisbon or Porto. Will it be difficult or problematic to exit the Delta Terminal 4 where I land and get to Terminal 2 or 3 for the later flight to Portugal? I assume I'll have to get my baggage and recheck in with the other airline. We would then both book a multi-city plane ticket arriving at Heathrow and departing from either Lisbon or Porto (which would have 2 layovers but bags would check all the way through) to come home together. Or would it be easier to book the roundtrip to Heathrow (just 1 layover) and just take the shorter flight to and from Lisbon or Porto on both ends? Having never been or done this, I'm sure there's something we're not thinking through. Thank you for any experienced advice!
As I understand it you're meeting your daughter at Heathrow and immediately flying out to Portugal. There’s no difficulty in changing terminals, providing you allow sufficient time, but if these are unconnected flights you will have to cross the UK border, reclaim your luggage and make your way to your second flight.
Bear in mind that if you arrive late at Heathrow and miss your onward flight you're on your own and a walk-up ticket will be expensive. Trying to add Heathrow into the mix in the way you suggest has its drawbacks
For you, I’d suggest booking a return flight from the US to Portugal (whether it's via LHR or another hub airport) and meeting your daughter in Portugal. This removes the risk of unconnected flights. Also, it might be cheaper or more convenient for your daughter to fly from another London airport to Portugal with a budget airline. You can still both fly back from Portugal to the US together.
Good points, thank you. All the flights to and from my home town are have two stops/layovers so just trying to decide if it'd be better to do that or have one stop to Heathrow and do the smaller flight with my daughter (which essentially is another stop, layover but more complicated I guess?) I suppose it would be better to just book the multi-city flight for both of us. Is there any reason to choose arrival and departure from either Lisbon or Porto, or round trip from one place?
Easy: Meet at your hotel in Portugal.
A little harder, meet at the Portugal arrival airport.
Most complicated, trying to co-ordinate a rendez-voo in Heathrow, a complex of terminal buildings.
I understand the desire for togetherness, but it comes with complications. You will have to retrieve your checked bag in Heathrow, go through immigration entrance and security procedures, find the second airline's departure terminal and check in ( which will have its own security procedures.)
If you flew from the Southwest to Portugal, you might find a non-stop, but even a transfer will be easier with luggage checked all the way through, and possibly cheaper. And for your return, you can fly on your own from a different Portuguese city. Your route should be set up by a multi-destination search function, saving time, stress and maybe some money. All of which you can focus on your offspring during your reunion. Enjoy.