Ravenloft Dhampir Traits

DMs,
I run a serious of one shots called If You Survive and each of my players get the chance to swap characters/items/feats each session. To my question -
What is your take on Dhampir Monk. Does the Vampiric Bite Trait supersedes the Monk Martial Art Dice?

In dndbeyond - the bite shows up in the Feats section and not in the Action section but shows up in the Other Section under all the different actions. 

Monk Martial Art Dice -  You can roll 1d6 in place of the normal damage from your Unarmed Strikes (this is from a level 3 monk)

(Vampiric Bite. When you use your Unarmed Strike and deal damage, you can choose to bite with your fangs. You deal Piercing damage equal to 1d4 plus your Constitution modifier instead of the normal damage of an Unarmed Strike.)

I would say that it doesn't supersede anything; it's another option you have when making an Unarmed Strike.

In the description of the feature, it says "you can choose to bite with your fangs", and then tells you what happens if you do: you deal Piercing damage equal to 1d4 plus your Constitution modifier. If you don't choose to bite with your fangs, then you deal whatever the damage would be if you didn't have this feature. For a Monk, that would be (at level 3) 1d6 plus your Dexterity modifier Bludgeoning damage.

If it said something like "when you make an Unarmed Strike, you deal damage equal to 1d4 plus your Constitution modifier", then you'd have to worry about which one supersedes the other. But it doesn't say that; it says you can choose to do it this way if you want, but you don't have to.

I agree. You can choose one or the other, but they don't stack.