Given the critical mind that led you to your current atheistic beliefs (what I did there? :P), you have to have developed a mature moral code. I’d argue that taking an oath on something at the core of your being would be more binding than taking one based on any external books or faith system. (Muslim here btw but I love philosophy)
Most people of faith don’t realise how most atheists develop strong intrinsic morality by necessity during their journey. And I’m not saying that all atheists are morally superior! (Humans be humans)
This is just an observation based on my experiences and discussions with most of the open-minded ones I’ve come across thus far.
Education beats indoctrination any day. And the well-informed believer has to go through an atheism phase (to varying degrees, so YMMV) to be honest with themselves. Doubt is a perquisite of developing independent morality that confirms faith. At least that’s what I believe.
Edit: also to anyone reading this, don’t ask me about religious stuff, I’m not an Imam or anything. Just someone who went through some heavy shit and had to think outside the framework to make their life work.