I was in your boat I have a 5 and 7 year old. Instead of making something
work , and ripping out your interior. Go with the GoWesty Rear Seat Belt
kits...they are a little pricey. But once I installed them, with the
instructions that they supply, and the directions are dumbed down. I have
problem recommending them. The drivers side was worth it alone....

My 2 cents...