This would seem like it would work pretty well. You might have to sand down the end of the Domino that would be sliding Br sliding into the mortise just make it easier to install and move the leaf. If this table will be old or given to others you might want to include replacement Dominos in case any was broken. This is where the simple tapered dowel might be more easily replaced by a non woodworker should the need ever arise.
Best,
Todd Ferguson
Harrisburg, NC