True Michael was unwilling to rely on anyone else to kill Sol and Mac because it was the only foolproof way.

I will have to watch that scene again but as I remember, it was short notice
They were panicking that they didn't know where the meeting was going to be when they were eating dinner

Suddenly if there is a lot of activity at and around the restaurant and more than usual men dining there even for the best veal in the city, I reckon it would attract unwanted attention

Also it is fleshed out in the novel, Sol had his people check the restaurant out, bathroom and all and a man was actually dining there, keeping watch

As regards a frontal assault, Sol could have had people guarding the restaurant too

That's my family, Kay. It's not me Michael ended up Mafia Don so there is no guarantee however all he wanted was after the law degree, Anthony can do whatever he wanted, to forge his own path but he got no support from Kay