Hello :)
Hmm I'm afraid I can't really help you on the school front - I've only just started looking into Kindergarten. If it helps, there seem to be a fair few bilingual Kindergarten here, but I think they are aimed more at Germans who want their children to learn English at an early age, rather than native speakers.
Saying that, there are loads of Americans here as the US Army HQ for Europe is here, or moving here soon, I forget. You will always hear American accents and English spoken in town but I shouldn't think it would be too hard to avoid.
As far as I am aware (and we've only been here for a year) the Americans are mostly here with the Army and tend to live in the Army accommodation. I'll ask my husband to check with his colleagues but I don't think there is a particular area dominated by English speakers.
Are you thinking of moving to Wiesbaden itself or would you be moving to somewhere just outside the city?
Wiesbaden is lovely, there just isn't really much going on, so it depends what you are looking for. For a more lively atmosphere you would be better looking at Mainz or Frankfurt.
Within Wiesbaden itself I think the nicer areas are Nerotal and Sonnenberg, but you will pay a little more to live in these areas.
There are some lovely areas (as far as I can tell) along the Rhine - I think Frauenstein, Sonnenstein etc. I haven't really spent any time there though so please don't take my word as gospel!
Sorry, after such a long post I don't think I've managed to give you any helpful information at all!
If there is anything more specific you want to know, or know the sort of area you are looking for (city, rural, etc) please let me know and I'd be happy to ask around for you.