I just gotta say - not sure how much use the in-motion satellite will get. If you're looking to entertain young folks, DVDs are a great answer. We purchased one of the Tailgaters version 2, mounted it on the roof, hooked it up to VIP211z (recently upgraded to a Wally) for about $600 installed. Friends of ours have Direct TV and quite honestly it doesn't come close to our Dish - way more options, way more HD.
Of course all of this is just my opinion. I would take the additional $2000 ($2600-$600) and buy other RV toys or gadgets.
US Army Retired - Loving The Road Trip