Those springs rates seem really high, especially for a constant rate.
I’d look into progressive rate springs or air bags. Those will be too heavy for DD, my opinion. I’ve got a built 08’ too, and I pull an off-road trailer.
If you can swing it, do White Rim in Canyonlands. Pretty secluded campsites. Pretty epic, did it in 2015 with my then 1,3,5 yr olds + wife. We've been doing a summer overland trip every year since. Ive found that stopping at random playgrounds along the way helped with the long car rides...
Thank you. We did another trip the following summer but this time we pulled a trailer with an RTT on it. Made things sooo much easier. Trip report here http://forum.expeditionportal.com/threads/161612-2nd-Annual-Family-Overland-Trip. So much to see in your neck of the woods!