Afraid I can't be super-helpful, but I did attend a wedding at the Park Hyatt several years ago and remember it being very nice. Also attended one at the New Otani earlier the same weekend, but it's a bit more impersonal over there (very big place with lots of banquet rooms--trying to find the right wedding can be tricky). If the Park Hyatt can do something for that size group at the budget you've stated, I think you can't go wrong with them.

And LapLap is right, if your fiancee and her family are not too fixated about auspicious dates you should try to avoid them in order to keep your costs down, although I think August/September are still less desirable than, say, October (as they're still pretty ridiculously hot).