Given the knowledge the Corleones had, if the family had insisted on Michael not being the trigger man, there would have been another way to get the hits done; an arguably easier way.

Have the plan unfold as before - have Michael agree to meet Sol and the Captain, minus the planting of the pistol in the bathroom. Place two unnoteworthy button men in the restaurant; ideally old hands who wouldn't stick out so much. When Michael goes to the bathroom, bada-bing, bada-bang, job done. Maybe Michael gets a little heat for being there but let the pain-in-the-neck innocent bystanders work to his advantage for once.