My main concern is this: would it be possible to have some of the five drive and/or ride in the Subaru? DH and I haven't gotten to the point of towing our Focus; I just follow him up to the campground (and listen to what I want to on the Sirius radio;)). Just an idea.
Also I doubt all five of you will want to sit in the camper that much. When our children join us, we're usually sitting outside, under the awning or anywhere. We cook over a fire because it's fun to and eat outside. We have all crowded indoors when it was too hot to enjoy a meal outside, but we don't stay there long.
And they drive their own car up. DH and I sleep on the dinette bed because we're shorter than our daughter and SIL and they have room for the little one and themselves in the corner bed.