I finally got around to figuring out a simple solution for mounting the iPad in our van. The mounts that attached to seat base were not going to work for us. Also, I wanted something that wasn't going to interfere with the cupholders, vents, or radio controls.
So, I used the RAM mount system and placed an Arkon disk on the dashboard so there was a place for a suction mount. It seems like it is going to work really well and is extremely sturdy. Here are the parts I used.
RAM Mount Diamond Plate with 1 inch Ball (RAM-B-238U) - 2 of them
RAM Mount Universal Tablet Mount Tab-Tite Cradle iPad (RAM-HOL-TAB3U)
RAM Mount Locking Suction Mount Base (RAP-224-1U)
RAM Mount Long Arm B-Socket (RAM-B-201U-C)
Arkon Circular 90mm 3M Adhesive Console Dash Base (AP020)