Re: 7,8,or 9 passenger van?
We have mini van and we are a family of 5 soon to be 6. One way we have combated the storage situation is a roof top bag. The soft ones so we can pack stuff of different sizes and not need to be a certain shape to close. Also it makes us really think about what we need to bring. I used to over pack! This last summer we took my husbands car on a road trip with 3 kids and 2 adults. we brought all we needed including cloth diapers and had room. We just needed to make sure we packed good. 4 days of stuff for us all and a stroller ect. All in a trunk.
My biggest advice is to get a van that is extended. My moms van is not extended and there is only enough room to lay a shoe box between the back seat and the van door. My van however has room to stow and go (older model) behind the back seat. Which means there is enough room to lay a stroller down between the back door and seat. And pile as high as you need!