The conjoined colonies wouldn't have had any strategic advantage in their plans against Britain, without the South Carolina colony.
There were probably plenty of other less timeless decisions he had to make.
I think reasoning along the lines of "this decision negatively affects X group in an immediately unjust way, therefore it shouldn't be done" is naïve and conceited. People who use this type of reasoning are either knowingly playing the "I'm more moral than you" card and incidentally causing a net worse situation in the future, or they are just naïve and don't understand that local immorality can lead to net positives in the future.
I'm not arguing that hard decisions aren't necessary. I'm saying that aren't as necessary as sometimes claimed, and should be viewed with some skepticism.
Slavery was more important to the southern economy, but slavery existed in New York as fully legal until phaseout began in 1799. It wasn't eliminated until the 1820s.
Monied interests in most states/colonies would have have permitted the loss of their property without compensation.
Many wanted the split from Britain to cause slavery to end. Nobody was proposing that it begin. Southern colonies insisted that they were going to continue slavery. If the north agreed to leave slavery unchanged, they would go along with the split, allowing other changes, and they would keep slavery. If not, they would not cooperate, there would be no split, no other changes, and they would keep slavery. Either way, slavery would remain unchanged.
The decision to leave slavery unchanged did not "allow slavery to occur".
There was no such decision to be made (or at least no such decision on the table).
The decision was whether to have slavery-permitting states in the US, or slavery-permitting states outside the US.