You supplied great information, thank you. I rechecked my sources so I can be accurate. Our Williamson Bible says it was given to Sarah Blake Williamson by her husband in either 1857 or 1859. That same handwriting gives Alonzo's (her husband) birth as 20 Dec. 1815 in Woodstock, VT. No vital records in Vermont confirm this date (or any other date). That same birthdate is given in the History of Cornish which gives a small biography of Alonzo. He was admitted to the bar in Cornish in 1837. It makes me wonder when he left Canada. Page 794 of the Mayflower Families tells that in 4 May 1832 Henry C. Dennison was appointed guardian of Elvira, Verona, Alonzo, Eleutheria, Lenora and Orwell, heirs of Polly Williamson. It says that is when her parent's estate was settled. It mentioned that Orwell and Lenora still needed mother's care, so that may have led to the breaking up of the family. Elvira went to live with her aunt in Constable, New York, so perhaps the other children went to other relatives.
This book gives the birth year of Lenora as 1824 and Orwell 1827, the year his mother died.
I keep thinking about your comment about them traveling north and south, I suppose there are little bits of information along that route! I noted in a sketch of Shipton that Nathan Williamson (among others) arrived before 1804. Some of those other surnames you have mentioned: Leet, Barnard, Harvey..