Here it is almost a year after you posted your message! however...I have quite a bit of information on Colonel Isaac Allen as I have a particular interest in one of his grandsons: Thomas Campbell Allen ( b.1860 d. 1921), a house builder in Fredericton, New Brunswick.
Just a short sketch: Isaac Allen first arrived in what is now Nova Scotia in 1783, spent one winter there with the promise of land but left for the Saint John River Valley in what is now New Brunswick ( still part of NS then) when it was discovered that good land had already been allotted to the "planters" over the preceeding 20 yrs. ( another story)
Isaac had one son, John, who was involved to a lesser degree than his father both in politics and the military. John married three times in the course of his life and had many children with his three wives. Generally, he lived in Kingsclear or Springhill on a large trace of land, part of his father's original land grant.
One of John's sons from an early marriage was John Campbell Allen ( b. circa 1828), who was trained as a lawyer like his grandfather and became the first freely ( demoncratically) elected Mayor of Fredericton. One of John Campbell Allen's sons, Thomas Carleton Allen, also a lawyer was engaged to a woman who set sail aboard the Titanic. Luckily, she and her mother survived and Thomas Carleton was in New York to receive her. Following a short recovery there, they hired a private rail car to take them to her family home in western Canada. Her father and a brother were lost.
MY interest is in Thomas Campbell Allen, a much younger half brother to John Campbell Allen and about the same age as his nephew ( John C's son) Thomas Carleton. They lived in the same small 'garrison' town but the two men lived very different lives: Thomas Carleton one of a good education and privledge, and Thomas Campbell one of hard work and family duty. He lived on the family farm until almost age 40, about the time of his mother's death. Thereafter, he had an interesting career building houses in Fredericton, particularly on Sunbury St. ( now University Avenue) . He made some interesting venacular structures following the ideas of the arts and crafts movement.
I am mid-research but have more than this brief sketch. I am hoping to find decendents of any of John Allen's many children or grandchildren to get a clearer picture ...