Try talking to him about it, but nicely. Explain how you two won't really have any alone time when the baby arrives, so why not take a break just for a day? Order some pizza, or go catch a movie. Keep your tone light so as not to upset his or pit him off. Point out all the things you already have, and how you two deserve a little something for such diligent efforts in preparing for the baby.
You could also say you'd like to celebrate the bright future you two will have with the little one with a night out or a day of resting in.
Just take a day off on the weekend and game charge! Tell him you're boss for a day and go do some fun stuff or even do nothing at all! No need to bring it up to create an argument just step around it.