Would have been closer for you to fly to Girona with Ryanair and it's also cheaper to hire the car there and drive up to Argeles. Not all hire companies will allow you to do this, some charge extra, but it's included with the Hertz cars.
It's not high season in Argeles, so you'll find a lot of shops, restaurants, bars etc. on the beach closed, but there are some who are open all year round.
Places to visit depend on what you like to do/see. [broken link removed]is a must - there's also a small market there every Wednesday and Saturday. Go early in the morning - parking is very, very difficult.
Ceret also has a good market, wine, cheese, fish, meat, clothes, shoes, etc. etc. on Saturdays - it finishes around 12.30pm.
Prats-de-Mollo-la-Preste is an old walled town around half an hour's drive from Argeles which is also worth a visit.
Villefranche de Conflent is another old walled town worth a visit.
If you like steaks, there's a good restaurant near Perpignan [broken link removed]which is also beside a bowling alley if you're going with kids (yours may be too young).
There are a few small supermarkets dotted around the village and seafront. The best one to shop at is which is on the road to Perpignan. You'll get everything you need here - fantastic selection of cheeses, wines, cold meats, fruit and veg, breads, etc. There's also a Lidl not far from Centre Beach - there's a map [broken link removed].
Lots of info and things to do on the [broken link removed].
Hope you enjoy your holiday!