Which hotel-got kids and near beach on budget?

Hey, Could someone help me find a suitable hotel please? I will be staying in Lisbon between the 5th and 8th of July. I have a 10 and 14 year old so need a hotel that is family orientated. Not necessarily a kids club or anything as they will be with me most of the days, but a hotel that stays away from the young, clubbing, partying crowd. It needs to be near the beach (walking distance) and as cheap as possible However I'm looking for a 3 star or more. An Apartment will also do. We are thinking near tamariz beach as I have heard this is most popular. But any hotels near the quieter beaches would also be great. Thank you