IIHS gives the Jeep Wrangler 2 out of five stars for rear passenger safety.
Unlike the IIHS frontal offset and side impact tets, the IIHS rear crash protection rating is not an actual crash test. It is a subjective evaluation of the geometry of certain seats (not all seats or variations are necessarily evaluated) and sometimes a dynamic simulation of how well the head restraints work. This is done for an average sized adult dummy at typical seat and head restraint settings.
So, it is completely meaningless for children in child safety seats with a 5-point harness or high back boosters, all of which provide integral head restraint.
As far as rear end collisions being rarer than front end collisions that won't matter if you are one of the ones involved in a rear end crash and your child is killed. I was rear ended at high speeds within just a few years apart and have never been involved in a front end cash.
Relative frequency of crash types are taken over tens of thousands of crashes. While your anecdotal incidents may vary, that doesn't change the statistics. For example, you may be left handed, but that doesn't prove that the majority of people are not right handed. In addition, sampling only yourself introduces other variables like your driving habits that could make you more prone to being rear-ended. These types of variables generally wash out with a large number of samples over a wide demographic.
Either of the crashes I was in may have beeen fatal had I been in a Jeep Wrangler with a child in the back seat.
Unfortunately, we have no crash testing that allows us to compare how vehicles fare in rear-end crashes. Jeep Wranglers may be worse than average or better than average. The size of a vehicle does not necessarily reflect how well designed it is to crush and absorb impact forces.
I would not allow my husband to haul my child in the back of one of these vehicles. One should not take the attitude in a case like this that it's not likely to happen or it won't happen to me. If it does, it's too late, and I think that's a too late none of us want to experience. It's just not worth taking that kind of risk with the life of your child.
If only we had a conclusive crash testing rating to allow us to know for sure. The reason we do not have this is because fatal rear end crashes are relatively uncommon. Most funding is therefore put into areas known to significantly reduce severe injuries and deats, like seatbelt use, impaired driving and crash protection from frontal and side impacts.