Travel Light Backpacks.


We are a family of 4 with 2 teenage kids travelling to Spain & Portugal in August for 11 days. We plan to cover 4-5 cities and travel light. Can someone suggest a good quality and durable backpack, ideal for this kind of travel, where each of us can have a backpack and not a rolling carry-on suitcase? We want to be able to go sightseeing as soon as we arrive at a destination city and not have to check into our hotel/apts for the sake of leaving our bags there. Thanks,