The mood is sombre for what you have to do to him, but you are also excited for your new relationship.
I, your Mother, have just been turned into a vampire.
Tell him what's happened to you and that you'll have to hurt him a bit.
Pretend to bite him just off screen by leaning forward to the side of the camera and put the collar on him to the side of the camera as well and tie the chain around your wrist or somewhere.
This is where you can talk kind of sad about his short life, like 'how you made your son' video.
I'd like to use the collar from your daddy video if possible.