In reply to tom_greenwich:
As promised here's a summary of our week in Font.
Climbing:
Buthiers - Was quite noise and busy, plenty for the kids to climb on and lots of sand to play in, although we didn't find any of the kids routes. Recommended if you are staying near-by or combine with a trip to the pool (which we did, yes you do need speedo style swimmers)
Roche Aux Sabot - Good kids circuit, although a bit reachy for a 4 year old. again plenty of sand and there is a nice walk in the forest. We were unlucky and visited at the same time as a large school group.
L'Elephant - By far the best of the 3 from a kids perspective, the climbs all edge onto a large sandy area which was great as I could climb and always see the family, there are also picnic benchs under the trees. Plenty for the kids to climb amongst the circuits and up on top of the hill there is a great kids scrambling/climbing circuit which was perfect for a 4 year old.
General thoughts - take a bucket and spade and a bug collecting kit, take a bouldering mat which the kids can use to jump onto, sit on, build sand castles on. There is a great patisserie in Mille. The chateau in Font is closed on Tuesdays (we learned the hard way!).
Buy a helmet for the kids, buy them decent shoes to climb in (not from decathlon like I did)
We will be going back!