Might suggest you try census on ancestry.com as it is free this weekend, although I don't know what years.Sometimes the actual census images have more detail as to month/day/year of birth.
It appears from 1860 and 1870 census George and Olive had many more children than you had listed/found who might be traceable.
Also appears that at some point in 1880, Olive is living with dau Fanny Bracket in NH, both widowed. No image of actual census on familysearch to see the actual date to determine Olives approximate date of death.
Not my family, good luck.
US Census, 1850 Palmyra, Somerset, ME George WrightM 34 ME Olive Wright F 30 ME George E Wright M 7 ME Fanny O Wright F 5 ME Benjn P Wright M 3 ME Eliza J Wright F 1 ME
U S Census, 1860 Palmyra, Somerset, ME Page:7
Family Number 41
Geo P Wright age43 Olive Wright age 40 Geo E Wright age 17 Fanny O Wright age 15 Benj P Wright age 13 Eliza J Wright age 11 Charles E Wright age 9 Angola Wright age 7 Nathan F Wright age 4 Henry R Wright age 3
U S Census, 1870 ME George P WrightM 52y Somerset, Hartland, ME Olive Wright F 50y ME Angie M Wright F 17y ME Nathan F Wright M 14y ME Henry R Wright M 13y ME
U S Census, 1880 Somersworth, Strafford, NH SELFFannie A. Brackett F 32 ME widow SONWalace C. Brackett M 5 MA SONGeo. S. Brackett M 3 MA MOTHOlive WrightF 60 MEwidow