Trip to Lisbon -- enough to keep busy for 6 nights?

Lisbon has lots for young ones to do. You don't say their ages so it's a bit hard to recommend activities, but our granddaughters were 10 and 12 when they went with their parents and us and they loved the Tower of Belem and Castelo Sao Jorge because they could run and climb. They enjoyed the Coaches Museum as well. We had previoiusly visited a lot of monasteries so we didn't visit the Jeronimos Monastery but you might enjoy it and the children would also have space to move freely. The children also liked going up Elevador Santa Justa and climbing the stairs the rest of the way to the top for a great view. Another fun experience was riding the tram and the funiculars. We took the tram as often as possible and rode the funicular up to a park, Miradouro de Sao Pedro de Alcantara which has beautiful views of Lisbon and gardens with lots of room to run around. We took a day trip to Sintra where they really enjoyed the National Palace of Pena for the same reasons. Pena also has a nature park where they enjoyed a hike. We also visited the Toy Museum in Sintra which even the adults enjoyed! We have visited places on other trips that your children might like if you have time. In Sintra they might also enjoy the Moorish Castle or Quinta da Regaleira. You can also take a day trip from Lisbon to Cascais for the beach. Or you could take the ferry across to Cacilhas; it's a fun ride with great views of Lisbon and you can then take a bus to the statue of Christ which you can enter and go up to the top. Another thing they enjoyed was the pastelarias, the pastry shops. I don't think you have to worry about getting bored in Lisbon and the nearby areas and it will be more restful for you and the children to not be moving hotels. As for missing out, we often spend 3-4 weeks in a country and always feel like we have missed out on so many things so we continue to travel. If you feel you have missed out by staying close to Lisbon just take it as a sign that there is more travel in your future!

I think you could have a great time staying in Lisbon for the whole trip, with side trips (Sintra, Cascais, perhaps...) Lisbon is a super place to explore on foot and by public transportation - the cable cars are fun, and the subway system is excellent. Three things I particularly enjoyed were the Monastery dos Jeronimos in Belem, the Museu Gulbenkian, and the Oceanario, Europe's biggest aquarium. The Gulbenkian is right near a large park studded with Botero statues (I could go on and on, but seriously, Lisbon is wonderful).

Great replies so far! I would add the aquarium, the zoo, even the huge Centro Colombo (shopping mall) is fun! You could also book a full day bus tour to Fatima, Obidos, Nazare, and Batalha which includes lunch. Lisbon is well worth a week, especially with some day trips.

Thank you all SO much for your input and ideas! These all sound great! My kids are a bit younger (4 and 1) but I think a lot of these would be great for them and it sounds like there's more than enough to keep us busy for 6 days/nights. Thanks everyone!