As the parent of a kid who doesn't look like me (and that's a very good thing), the recommendation above is perfect.
Only a parent can understand self sacrifice. And only a grandparent understands from a generation away.
If you must purchase something...
Get her a car seat for her jeep and get him a jogging stroller.
Go to "once upon a child" for lightly used items.
I was thinking the same thing. As a parent and grand parent I can tell you we hate to see our children spend money on gifts. I would much rather them not spend money (they always do it anyway) that they don't have to blow....and just give us something small with meaning.
I will never forget when my daughter handed my wife a $2 baby bib that said something about best grandparents ever.......I didn't understand what was up until I seen my wife crying like a baby and showing me......that was pretty special.
I am sure your parents will be happy with whatever you give them....it sounds cliche, but honestly you being what you are has already made them happier than they could ever be.