hope this may be of some help and i hope that others may have info to help kick start your tree.
it took a while to find your donald on the 1841 census as he was transcribed under Daniel!!!!
1841 census; lochend, aberfoyle
donald...age 35...ag labourer
mary...age 35
john...age 11
donald...age 6
margaret...age 1
1851 census; tonmagarrow, port mentiith
donald...head...age 46...ag labourer...born aberfoyle
mary...wife...age 48...born arrochar
mary...dau...age 11...born aberfoyle
margaret and mary are interchangeable
1851 census; port menteith
john...age 20...servant...ploughman...born aberfoyle
1861 census; gartmore village, port menteith
donald...head...age 56...ag labourer
mary...wife...age 57
jean...grand-daughter...age 8...born kippen, stirlingshire
happy hunting
Joe