After James was born, would both George and Winona have remained in Starfleet, or would one of them have resigned their commision to care for their kids?
We don't really know that Winona would have been in Starfleet payroll at any point, now do we? She was wearing civvies the only time we glimpsed her, and wasn't addressed by rank.
Spock Prime confirms that George Kirk Sr. lived to see little Jimmy become a starship captain, and inspired Jim to do so, but that tells us nothing about George's career as such. This does mean Jim's parents weren't slaughtered by Kodos the Executioner, or at least his dad wasn't, which really raises the question of why Jim would have faced Kodos alone. What possible reason would George Sr. (or George Jr. for that matter) have for survival if not absence from Tarsus IV?
If we are forced to assume absence of parents, we probably have to assume Jim was an independent sort of character. It doesn't sound as if Tarsus IV would have been running a summer camp for Starfleet kids or anything. Had little Jimmy left home behind at that date already? Also, why is it that he got his sponsorship (or other backing) for entry to Starfleet Academy from Ensign Mallory's dad, and not from his own? Would sponsorship from relatives not be accepted?
Did Winona or George ever have anything to do with Iowa, or was that just a Jim thing? Or Uncle Drunk thing?
Lots of questions there. Lots of noncanon answers that no longer quite fit the evidence...