Reuben is probably the right age but the 1850 census from Cortlandville, Cortland County shows Henry and Eliza with a bunch of kids that don't include Rueben. Daughter Mary (19 yrs) and son George (17) were born in Massachusetts and the rest of the kids were born in NY, hence the move date of about 1835. The remaining children are Amos (14), William (12), Daniel (4), and Philo (1).
Reuben would have been 2 years older than Mary, certainly a possible oldest son because I don't know when Henry and Eliza were married. Have you found Reuben in 1850? I can't find him then. Interestingly, the Olds family that shows up in Great Barrington in 1850 is one of mine- Ozias Olds - which makes me think there is probably a connection between this "Amos Olds" line and my "Seth Olds" line that ended up in Alford. Either that, or there is a bunch of erroneous information in the "Olds Book", which ia also where some of my info comes from.