hello jmg1
If I were you I would stay somewhere in the centre, Emilia Romagna, Tuscany, Umbria, Lazio, Marche are all good places to live.
Yoiu will probably need to live closer to some of the larger towns if you want English schools. As far as I know there is none in Umbria for example.
Re aupairs, lots of people I know in Italy use 'nannies' for childcare, but they tend to be eastern european, non qualified ladies who work for quite small wages and will do just about everything (cleaning, cooking, childcare, etc), in general they're v. good and hardworking, but people find them by word of mouth as far as I know.
re house, it may not be easy to find as Italians live in flats mostly, or villas when theyc an afford it, but you might be lucky. If I were you I'd go and explore a few places before making any decisions, and if you cna get someone who can help you with tghe language when house hunting it's preferable as in some places people may take advantage of foreigners who don't speak italian, especially if v popular like Tuscany
best of luck!!!
Sorry I wasn't much help, I am Italian but don't know much about practicalities for moving there.