Don't panic! Be happy....
I lived in Toronto for about 3 years and LOVED it - it's a fab, safe, family-friendly city with lots to do, and Canadians were all very friendly.
I should say however that I was single when I was there, but still have lots of friends who have raised their children in the city or in the nearby suburbs.
Does your DH's company not offer some sort of relocation advice/ contact - ask for this, it's pretty standard with most big companies. They would be able to help you out with questions about GPs/ health system etc (I seem to recall it's more insurance based than the UK, so you will probably need some kind of medical cover).
Re Areas - the Toronto Transit system (their underground/tube) is very efficient, and it means that even in the suburbs you can get into the city and round and about very quickly.
Good areas to look at are:
Rosedale (for the wealthy, rich & famous etc)
Yonge St is the main North/south street and many of the areas going North out of the city off Yonge Street are nice - leafy & full of families
e.g. Yonge/Eglington
Yonge/St Clair
If you fancy something a bit more Boho, then the 'Beaches' area down on the Lakeshore is fun, with lots of artists and musicians and interesting shops and cafes.
Seriously though, I am very - you will have a GREAT time!!