Portugal in February with young teens

Highly recommend the Oceanario in Lisbon. It compares favorably with the major aquariums I've seen in the States, and is easy to reach by subway.

Hi Trish,
The 3 things my teens remember most:

-We took the ferry across from Lisbon to the area directly across where there are restaurants that have seafood (sardines, etc.), the whole experience was amazing. Took the metro back.

-We rented bikes and rode from Lisbon to Belem along the water- bike path the whole way- easy and flat and beautiful, it felt like an adventure even though it was really simple and fun.

-We took all the transportations we could find- elevators, trams, bus, metro, train, etc.

I can provide details if you're interested, and we weren't there in February, so I can't help with the weather info. Whatever you do, it'll be great.
Robert in Montreal

I especially like the Gulbenkian Museum is Lisbon. It's one (rich) man's collection and has a bit of this and a bit of that, not just paintings. It's not huge, so you don't really have time to get bored.

The Manueline architecture of the Jeronimos Monastery at Belem (Lisbon area) is distinctive enough that it might be of at least passing interest to your children.

Lisbon is hilly, so just walking around the city can be quite a hike.

Given your interests, here are some suggestions.
I recommend making Lisbon your base. The algarve is known for beaches, but it's chilly in February.
In addition to the aquarium mentioned earlier, Lisbon has a good zoo. I have not been there recently, but they used to have an impressive marine mammal show.

If your kids enjoy castles, I highly recommend at least one day in Sintra (easy day trip from Lisbon on the train), and particularly exploring the gardens of the Quinta da Regaleira. Be sure to bring flashlights for the caves.
Cascais is a good day trip. There are good beaches there, but February is not good beach weather. When in Cascais, you could walk out to Boca da Inferno. It can be impressive if there are big waves.
I recommend the electricity museum in Belem. Most kids find it fascinating.
I also recommend the number 28 tram, which is in every travel guide.
No problem finding good food in Lisbon. I like Rick's recommendations, and also the Trip Advisor website.

thank you everyone for the great input!!
Notes taken! Keep the info coming if anything comes to mind!!