We gave $100 when we had the twins baptized (FIL gave $50; we gave $50) however; when Logan was done we didn't b/c we honestly didn't have the money. FIL always makes large donations to the church though.
I'm sure this was unique for a Catholic Church but when we baptized dd we tried to give a 75.00 donation. The preist gave it back to dh and told him to put it in the babies college fund instead because it would do her more good there!
We did both. My dad made a donation to the church that the kids were baptized at ($100 I think). Then with DD we also gave th priest $100. With DS we didn't not give money to the priest. However, the priest is my uncle so we gave him a more personal gift rather than money. If he was not a relative we would have given money for both.
Re: If you baptized DC
We gave a check, made out to the priest, right before the baptism. It was easier to just give it to him then.