I agree that a wedding that takes place in a church is most definitely religious as well...
It's your son's baptism! Even though there will be wine, I highly doubt that anyone will be getting sloppy drunk at a baptism reception...People just don't do that!!
I really don't think you have anything to worry about there. Guests will probably just have one or two drinks with their meal or hors d'ouevres or whatever you are serving.
The alcohol usually served at a wedding is saying "hey, have a good time!!" The alcohol served at an event like this is more like "have a glass of wine or enjoy a beer with your meal."
Catholic baptisms take place when the child is still a mere infant.