>>I have some time before we can so can brush up on Portuguese basics too.
Don't worry too much about learning any Portuguese, at least for speaking. Maybe "Obrigado" or "Olá, fala inglês?", but anything else invites a response, and if by some chance they do respond in Portuguese to what you managed to ask them, realistically you won't have a chance of understanding that reply, so then it's back to English and you've just cost everyone some valuable time. Also, people in Portugal speak good English and have a much easier accent to understand than say Spanish people. It's more important to speak clearly in English and maybe use a couple more words than usual, e.g. "We would like two more beers please" rather than "Two more, pal". And "Hallo, do you speak English?"
If you're going to study any Portuguese, try learning some signs and other things that you might see, or perhaps menu items --- although most of the time you will be seeing menus in English, but sometimes the translation can be spectacular. Learning some names of dishes can be helpful.
Portuguese food can be surprisingly plain by Mediterranean standards (OK, it's not on the Mediterranean), which can be an advantage with children. I tend to eat pork rather than beef (which often isn't great). There are lots of soups. A nice plain-ish one is canja, which is chicken broth with rice (plus whatever the cook wants to add today).
What kind of transfer have you got arranged from the airport to your accommodation?