Hi Cath! Welcome to the board!
There is a difference in type of accident. NHTSA has established replacement guidelines. Some seats follow these guidelines (namely Britax, Combi with at least its Coccoro, and Sunshine Kids with its Monterey -- but not Radian,) but many seats are required to be replaced after "any" accident (Graco, Evenflo, Cosco/Dorel.)
The first thing to establish is what type of accident it was. The NHTSA guidelines are
here and are as follows:
Minor crashes are those that meet ALL of the following criteria:
*The vehicle was able to be driven away from the crash site;
*The vehicle door nearest the safety seat was undamaged;
*There were no injuries to any of the vehicle occupants;
*The air bags (if present) did not deploy; AND
*There is no visible damage to the safety seat
If any one of those criteria is not met, it is a major crash and ALL seats in the vehicle must be replaced.
If all of those criteria are met, next you move on to what seats you have. You should look in your manual and find the section that talks about replacement after a crash.
If you need help determining the severity of the crash or whether your particular seats need replaced, please post more details (description of crash, seats that were installed) and we'll be happy to help you determine it.
If you determine that your seats need replaced, insurance should pay for a replacement. Depending on your company and your adjuster, you may have a fight on your hands, or it may go smooth as butter. Personally, I got eight seats with an aggregate value of over 1k replaced without a fight, despite the lack of visible damage to the seats, but my crash was fairly severe and I was pretty no-nonsense in talking to the adjuster, ie, "I had eight seats in the vehicle, how do we go about replacing those?" and then providing the company the information they needed.
Sometimes insurance companies will require the old seats -- mine wanted the shells left with the (totaled) vehicle, but was fine if I took the covers and any other reusable parts. If your MIL's insurance co doesn't want the seats, then they should be destroyed. Straps cut, covers removed, shells mashed up with a hanger or at minimum, having "CRASHED! DO NOT USE!" written all over the shell in black marker. The parts should be put out in dark trash bags over several weeks to dissuade dumpster divers from retrieving and attempting to reuse your unsafe seats. (This is the same protocol to use when disposing of an expired seat, BTW.)
Some areas do have seat recycling programs, but I don't know which ones. (Mine does not.)
Let us know if you'd like suggestions for replacement seats -- it's most helpful to have the children's ages, weights and heights, as well as the vehicle that the seats will be going into.
Hope that helps!
