Uhhhh, in Colonial America, many times children were ALL baptized at the same time when the family joined the local church. I have just completed adding 5 children to a family who all were baptized on the same day.
We don't have birth dates for them, just baptisms, but I put the Baptism date in the birth field and click the "Before this Date" button. Sometimes I have to go back and interpolate the birth date, but it is always before the Baptism date.
(Now someone can write in that the above technique is wrong....)