Well, I hope you had a fun packed day. He must be bursting with excitement for the evening ahead.
Start tonight as you did last, with a bath including plenty of teasing. Get each other nice and clean, everywhere. Clean his arsehole with your finger, and just slip the fingertip in, to give him a hint of what is to come. Do the same to yourself, in a way that he can see. Tonight, you will take a little more control, but he will not know what is you, and what is instructed through this tease.
Once you have finished your bath, ask him to get into a pair of your panties, or even better, if you took him shopping, his very own pair! Again, tell him to meet you in the bedroom. You put on the sexiest underwear you have, again ideally what you picked out today shopping.