Can't help you with which model would be best for your family.
Price...negotiate somewhere between 20 and 30% less than what they are asking...
Shop different dealers (even nationwide) for the exact model and options you decide on and use their prices as leverage.
I think the prep fee is complete baloney...It's their job to "prep" what they sell and I wouldn't pay a dime for it. (Ever pay a "prep" fee for a new car?)
But, regardless of any add on fees the dealer may want, the bottom line pricing is what counts.
And, don't let them muscle you into an extended warranty..they will certainly pressure you there and also for a paint and upholstery protection package.