Car seats generally expire 6 years after manufacture. So the one seat will expire 12/12/09, the second 4/14/10. From an age perspective, the seats are fine. Just be sure they haven't been in a crash or anything.
As for the CR report, ignore it. CR reviews are so out of touch with reality, that they should just be ignored. Do a search on Consumer Reports here to see why none of the techs respect their opinions.
I know nothing about the seats you SIL has, but hopefully Julie or another tech will jump in with some suggestions!
HTH!
Sarah
Mom to Alex (2002) and Catherine (2003)
"The challenge of parenting isn't shaping your kids to be what you want, it's shaping yourself to be what your kids need." - Wellyes