。。
Dinner's wherever you like. I'll leave it to you.
Literal
Dinner [topic-は] anywhere mind-not-[polite-ません]. [humble-お]-entrust-[polite-します].
A gracious, trusting response. どこでも ('anywhere') built like the pronoun series (何でも, いつでも, 誰でも). 構いません ('I don't mind, it's fine') is the polite negative of 構う ('to care, to mind'). お任せします is the humble-polite form of 任せる ('to entrust') — a set phrase for 'I leave it up to you,' used when giving the other person full decision-making authority. Extremely common in restaurants where the chef's choice is called お任せ.