Update on the Alps trip that I asked about in the OP. We found an apartment in Bourg St Maurice and had two excellent weeks, I’d really recommend it as a base for a family/riding holiday.
Obviously everyone is different and wants different stuff but staying in Bourg gave us the best of all worlds, we could get the funicular up to Les Arcs or easily drive to Tignes/Val D’Isere but we were in a town that had a supermarket and access to road rides etc. Both Les Arc and Tignes/Val D’Isere had a good trail system of marked/lift access stuff (the Tignes lift pass was free (!), Les Arcs was 72 euro for the week). The 50m pool in Bourg was lovely and being in the valley there were flat roads/trails for running or easy rides.
Road rides were good, the Cormet de Rosalend was lovely as was the Col De Petit St Bernard and there were lots of other smaller roads on the valley sides, or you could do the climbs up to the main ski resorts (but these had quite a lot of traffic).
Kids wise the green (and some blue) DH trails were great for our 5 1/2 yr old son, just for being able to ride with him in the Alps it made it the best holiday I think I’ve ever had.
Thanks for the tips and advice. If anyone is planning a similar trip I’d be happy to give more detail.