Luke wouldn't lay a hand on Anakin until Anakin mentions Leia. Though knowing Anakin's unwavering stupidity - he probably would. And Sidious gave Yoda a run for his money. If Anakin and General Grievious AND Sidious took Yoda on, it would be a slaughter. Yoda would be distracted by Grievous and Anakin - and Sidious would throw a micro-Senate pod at Yoda and crush him.