Not sure if a "christening" is exactly a place you want to take a first date. Probably better to take her out some place you two can get to know each other more easily.
I asked this girl out 2 days ago and my little cousin has this crising or what ever it's called and should I ask her if she would like to come with me.??
Do you mean a "christening" ... Like a church function?
If so ... Unless you attend the same church, and she is friends with your family - I wouldn't recommend it.