Free opinions from everyone - and all reflect our perspective and expectations.
Your trip will be enhanced with an Interstate vs a mini-van or suburban. We've towed a trailer which carries bikes and gear, and the kids and dogs have enjoyed camping in the trailer when they aren't sleeping in the tent. Gives mom and dad a break from kids and kids a break from mom and dad. You're "together" but not on top of each other.
Rear ride - geez, do you remember your dad asking if the ride was back in your family's 1969 Country Squire station wagon? Ok, I'm dating myself. We've owned a 2014.5, and now own a 2016 nine passenger ext. The ride is fine and only under more scrutiny now because of the new air suspension's availability.
For extra safety features, and possible resale reasons, I'd purchase a 2014.5 or newer. Easy for you to resell next year if you choose. Inter blog will tell you to get a 2010 and upfit it, someone else will tell you to buy a 1983 and polish it (I'm making that up) because we all have a different perspective. Our family bought a new 2014.5 in 2014, put 26,000 hauling kids around North America touching everywhere from our home in Jackson Hole, back home to New Hampshire, Baja, Banff, Quebec, Charleston, and finally to our new home in Bend, OR. We sold it for $11,126 less than we paid for it, nine months later. Several people interested in buying it because of the additional new features of the 2014.5 model, including the new MB chassis and multiple air bags.
So - buy what you can afford, or justify, and just know this huge Suburban will carry your family safely anywhere. It'll offer a potty, change of clothes, shower, and an adventure platform unlike any other. And you're likely going to be able to deduct interest payments on the AI if you choose to finance and qualify it as a second home.
Not to mention, it's the perfect place to catch a nap in between those soccer, lacrosse, skating or other tournaments.