Where to rent comfortable flats in Barcelona

Planning a vacation to Barcelona with my family for about ten days. We really want to skip typical hotel rooms because eating out three times a day with kids gets exhausting and expensive. Having a fully equipped kitchen, a washing machine, and a separate living room makes daily life so much easier. At the same time, I am nervous about private booking portals because we had a bad experience last year where the host canceled at the last minute and the flat looked nothing like the pictures. What are the best options for verified, reliable holiday flats in central areas? Are there reliable companies that manage whole buildings with on-site staff?