In reply to jethro kiernan:
Orlu is a nice peak, at about 2200 metres. On the east/south sides, long climbs up to 1100 metres, but the path on the north is a very pleasant amble up through woods and alpine meadows. There's a reasonably pointy summit, so it feels like a peak, but without any actual climbing or exposure. Great views along the valley.
The one tip, if you're staying in Foix, would be to make an early start, to get across Ax-les-Thermes before the tourist hordes snarl it up. The return journey in the afternoon is usually much less hassle and you could stop to rest achey feet in the hot spring pool in the town square. Kids love it.
Alternatively, if the kids are over 1.25 metres, you can take the ski lifts out of Ax (the first section, out of town, is in a cable car and isn't height restricted; it's just when you get to the ski resort above the town). These put you high up on the hills without any real effort, and you can walk down. Just watch out for the MTB downhillers.
Martin