Hi Jac -
As Willow said - i'm also quite positive it is placed on as part of the ceremony.
In the later sacraments it is worn for the whole thing, but i think that is as you are already a member of the church so to speak. Alexander's baptism is this Saturday - i'll pop back in and let you know if you like.

I think just having minimal guests is ideal - it's not exactly something that needs to be celebrated by everyone, just you as his parents and the godparents and all of you celebrating the journey that you will take with your son. IYKWIM.

No idea on the prayer either - the baptism on Saturday is apparently quite large - so i can have a listen and see if i can hear anything appropriate? Though i might be a bit too busy :P