Went there last two years with young kids. Collioure is a must see town by the sea (Matisse, Derrain, etc lived there), great in the evening. See the Museum of moden Art in Ceret (30 Mins west of Argeles). Castlenou is an hour away, 10th centuary castle/town on top of a hill, kids will love it. Center of Pepignan is worth an afternoon shopping. Elne is a nice town 15 min away. Carcassonne castle is wonderful if a bit too touristy. Narbonne is a must see town over an hour north east. If you have the stomach for a twisting journey head south towards Spain on the coast road towards cerbere, it will take longer than looks on the map and may be worth heading back to France by the A9 (stop in the Dali museum in Figueres). Le Racou is quiet end of Argeles is nice in the evenings for a stroll.