What choices did Michael have not to become the Don?

"Vito's desire to make the Corleones top Mafia family again"
I believe Michael had little or no choice in taking over the Donship because it seems Vito [Corleones] needed to re-establish their glory, standing, reputation etc. that they are not weak and crumbling like everyone thought

Vito could have cut their losses, handed the business over to Clemenza and Tessio and let Michael try to start a new life away from Mafia

Vito planned all the dirty work - killing of Carlo Rizzi [for Michael to make his daughter a widow] and Moe Greene, the baptism murders - for Michael to carry out after Vito's death thus leaving a murderous legacy for “I never wanted this for you” son

Sure thing “It was Vito who chose the Mafia way for him”
“He was tutored by Vito longer than a year for Donship” before was even allowed out! to go and see Kay

“No doubt he liked the absolute power of being the Don afterwards”
Power tends to corrupt and absolute power corrupts absolutely [Sir John Dalberg-Acton]