I can't attempt to give a solid answer about opinions of the war, but the 1860 census lets us get an idea of the numbers. In 1860, there were a total of 110,251 people in the U.S. over the age of 80 (born before 1780) living in the U.S., and 16,416 of those were over the age of 90 (born before 1770). The war was from 1775 to 1783, so all of those people were alive for some portion of it, and a smaller percentage would have been alive for all of it or have had any real memories connected to the war period. Further, a significant portion of those people would have immigrated after the war, and some of those living in 1860 would have died before the Civil War started in 1861.

In the previous year, there were 9,622 deaths in the 80-90 age range and 2,864 in the 90+ range, so assuming that was constant into the following year, this brings our totals to 97,765 born before 1780 and 13,552 born before 1770 who were still living in 1861. The population was about 15% foreign born, so if we can assume that this was evenly distributed by age (a risky assumption, but for these purposes probably okay), that gives us roughly 83,000 people who were living in the U.S. in both 1780 and 1861, and roughly 11,500 of those were living in the U.S. in 1770.

Source: Population of the United States in 1860; compiled from the original returns of the eighth census, pages xxviii, xiv, 597

Link: https://archive.org/stream/populationofusin00kennrich#page/596/mode/2up