Magic number is 10, but could be 9 through tie breaker. At this stage of the game, you can't use tie breaker in a magic number situation - way too many variables to interfere. Magic number typically suggests you've moved past tie breaker... which means 10 is still our number.
We could clinch shield while on the field in NE, while the match is still on. If we beat LA and MTL, we gain 6 points.
If NYCFC lose in COL, and then in HOU on the Saturday, their game would finish around halftime of our NE game. In fact, they dont need to lose both, a loss and tie plus our 2 wins would equal those 10 points to give us our magic number.
Atlanta has 10 games left, 8 at home in their new stadium. Montreal is not making the playoffs... and Atlanta even finish as high as 4th (though a stretch to do it).
Here's a conservative outlook
Win in LA.
Tie home vs MTL
Lose in NE
Win home to NYRB
Win home MTL (this would land us at 69 points)
At Atlanta...who knows. I would be surprised about a tie or loss.