You want to fuck your friend's mom, who is like your mom and keep a moral character. Meaning what, you want to drink but dont get drunk? Or a better example is, you want a circumcising but want the foreskin, right?
Stop kidding yourself, having a thought of sex about a lady who is like a mother, already you have lost you morality. Losing morality is like losing your character. We dont give tips of seduction here, but I can suggest you to go ahead and fuck her. You already have lost your character by assuming her nude, now no point to act like a saint.
Next time we will call you Charan the characterless.