I'm looking at the same problem as you expressed, but I'm on the other end of life. I'm 63, it is my lovely wife that worries, and I'm looking at running the west coast of North, Central, and South America. I'm totally green at crossing borders, never had a passport before, speak nothing but English (and a few swear words my co-workers taught me), and if I don't do it in this next year, it will not happen. Ever.
My advice might be to tell your mother to get her own motorcycle and come along if she will behave herself, be a good traveling companion, stay out of the bars, keep her judgments to herself, be quiet when asked, and go home when she doesn't like it anymore. But that's just me. Would I dare say such things to my wife? No! To say things in such abrupt terms would define her (to herself) as someone who is separate from my heart, and that I will not do! But, I ramble.
Good traveling companions who will help you stay out of trouble are hard to find. Mine are mostly old or dead now, so I'll just pass along my best wishes for a safe adventure! Jerry.