First bath! How fun!
I'm sure you are going to have bunch of suggestions and I'm sure I will learn a tip from other on YT.
Here is my suggestions. Just use the parts that makes sense to you.
Before you wash them try to get them used to the sound and feel of the blowdryer. You can start by having them in the bathroom while you turn it on. Turn the wind toward them just a little in a playful way. Believe me getting them used to the dryer first will keep your tears a bay. Don't want them wet, cold and scared!
I bathe my girls in the kitchen sink. I place a rubber tub mat on the bottom of the sink so they get a firm grip and not slip.
For the first bath, I like to keep the faucet running in a low trickel so they get used to the new sound. I can also add more warm water as the bath water cools. Praise them a lot!
Add a couple of inches of warm water and use a plastic cup and start pouring water over their body. You might want to skip the head the first time just so they get used to the idea. Go slow and try not to let the water cool too much cuz they get chilly pretty quick.
DON'T EVER LEAVE THEM UNATTENDED! They are Yorkies and they WILL jump! They have no concept of hight especially when they are that young.
You are so going to laugh when you see him go into the after bath frenzy!
Let us know how it went for you!