Hi Debra
I have walked the Camino Francés with my mother twice, she was 79 the first time and almost 82 the second. We used pack transport services both times, and they really made all the difference. She could not have carried all her own gear and I could not have carried hers as well as mine. We used Jacotrans the first time and Correos the second and both were great. Correos worked out much cheaper for us because they have a different pricing system which happens to advantage slow walkers like us if you book a few days ahead as we did. But it's also very easy to use them day by day as with Jacotrans, and we had zero problems with either company. You only need to know where you'll stay the next night, and as others have said I think you'll find it quite easy to decide a day or two ahead where you want to stop - you will get to know how far you and your grandmother can/want to walk each day, and will want to check that there is somewhere you can stay that is roughly at that distance. I think a lot more albergues as well as other types of accommodation have opened since 2010, so you have more options. In our experience, just based on our preferences and physical limitations, it was better to walk slightly shorter days than we probably could have managed, than to push on to our limit and possibly overdo. But either way, the transport services enabled my mother to walk the Camino, simple as that.
Buen Camino to you both!