Seven kids means NINE people... That's either 3 or 4 more than the seating capacity of the truck (depending on whether it has a front bench or front bucket seats. You're going to be towing the trailer with a second vehicle following if you intend for everyone to have a seat belt.
Here's some things to consider:
The truck is a 2009. It's already 11 years old. There's no mention of mileage or maintenance records.
The only mention of a tow package is "with 4 pin connector" so I'd suspect the truck isn't "OEM equipped" for heavy towing. That coupled with being 11 years old ???
It's equipped with a "full size TEMPORARY spare tire". That's definitely NOT what you want on the ground with your family in the truck and any heavy trailer hitched to the receiver.
That 5.7L "hemi" coupled to a 3.21 axle isn't going to be "happy" with a 7500 pound trailer in tow.
Now, here's the "kicker" at least for me: The RAM builder site DOES NOT list any crewcab 5.7l "hemi" 4x2 truck with 20" tires and a 3.21 rear axle ratio.
http://www.rambodybuilder.com/2009/docs/dr/mlup1500.pdf
So, I'd be very reluctant to take that "dealer's vehicle features" list as reliable....
Bottom line, at least for me, that 11 year old truck is, at best, a marginal tow vehicle for a family as large as yours (even with a second vehicle) while towing a 7500 pound trailer.
I'd keep looking, and I'd urge you to look at 2500/3500 series trucks. As your family grows, you'll need all the cargo capacity you can find, beg or steal to stay under the "dad, can I bring...." requests that will only get heavier as the kids get older.....