The best bet is hand-written notes by your friend:
Dear Johnny and June,
Bubba and I will celebrate our sacramental marriage on Friday evening, April 4, starting at seven o’clock, at St. Rocco’s on 512 Westwood in Springbranch. We will have little Estelle baptized in the same evening. There will be a small reception after the ceremonies in the parish social hall.
We hope you can be there. Please let me know by March 31st.
“Hand-written” does not mean she has to sit down and write them all, but should sign them all herself.
Generally, the proper way to invite people to a baptism is via one’s informal notes or social card, with the event(s), time and date on it.
If the above doesn’t work, use the standard third-person invitation for a formal wedding:
The honour of your presence is requested
at the sacramental marriage of
Mabel Marie Kumquat-DePew
Bubba George DePew
and the baptism of their daughter
Friday, April fourth, two thousand and eight
at seven o’clock in the evening
Saint Rocco Church
512 Westwood Avenue
Saint Rocco Parish Center[/RIGHT]