They all turned out to be Ty beanies, which made this whole process much easier. I undid the stitching in the back and removed the beanbag (some are attached and had to rip out a few more stitches to release it.)
The blue teddy had bean bags in the hands and feet in addition to the butt bag. I unstuffed teddy completely (except the nose due to embroidery) so he could get a good washing.
I made rice / lavender bags to match the bean bags that were there originally. I did make the rice bags slightly larger so there will be more warm area.
I filled the bags about half full (like the original bags) with mostly rice, maybe 1/3 lavender.
I put the bags in the arms & legs first, put some stuffing in the tummy first then added the rice bags and more stuffing on top. Stitch the back closed again and they are ready for 30 sec in the microwave and a snuggly car ride. The kids enjoyed them. The lavender helped calm the baby down for a peaceful car ride and they even like sleeping with them!
PS. My eldest requested one of her little care bear toys be converted. This was not a Ty beanie, and is a very small toy (no bigger than my hand). So we took out all the stuffing from the body, leaving the head and legs stuffed. We stuffed it with plain rice (she didn't like the lavender scent, and no bean bag for this one) using a pencil to get rice into the arms. Then we stitched up the back nice & tight so no rice escapes and it was ready for use - start to finish - 1/2 hour.