The link posted above doesnt always work for me - the info about APs sometimes disappears so:
There are 3 types of annual pass
Francilien - 89
Fantasy -129
Dream - 179
It is the same price for adults and children but at the moment there is an offer on to get a free AP for under 7s.
The Francilien pass cant be used on day 2 and 3 after first use. The other 2 can be used immediately. there are blackout days on Francilien and Fantasy - days you cant use it and these are listed on the above link as well (this bit usually works)
the discounts available are better with Dream but only one person in the party needs this to get the discounts. The other big plus with dream is entry to EMH if staying off site but this is only for person with this AP so all need it if want EMH.
We bought dream last year and they have more then paid for themselves with entry to the park, discounts on hotel rooms, in shops and restaurants
Hope this makes sense. Please ask if you want more info