Hi

We got married in the Hunter Valley a few years back - so did exactly what you guys are doing in terms of looking for accomodation etc for guests! We also go there every year for our wedding anniversary, so have stayed in a few places

First thing is - you will find that in almost every place in the Hunter, it's a minimum 2 night stay over the weekend... they will all have packages etc so you'll find it won't be too much more than the one night.
From memory, I think one of the only places at the time that allowed you to stay only one night was the Crowne Plaza. You'd think the Crowne would be expensive too... but actually it's one of the cheapest places to stay up there

We've stayed at The Leisure Inn (lovely - self contained little villas that are spread across the property) - you can get studio, 1 bed, 2 bed, 3 bed... they have their own kitchen, etc. We had lots of guests who had children, and almost all of our family stayed at this resort & its definately kid friendly. They have a pool as well.

We've also stayed at Cypress Lakes Resort (that was where we got married) - super pricey to stay there if you book within the resort itself... but up along the top, there are villas owned privately that you can organise to stay (nothing to do with the resort) - and it's really reasonable. They're 2 story villas with either 2 or 3 bedrooms, same thing as far as kitchen, little lounge area etc.
If you're interested in this one, PM me and I can give you the details for the owner of the villa we stayed at last year

The other thing to keep in mind is to probably try and book asap. They have some type of concert or day on the green/ jazz in the vines now almost every weekend, and accomodation is getting harder and harder to get if you don't do it in advance... can you tell we stay up there regularly?!