I know this may be a sensitive subject but could someone guide me in the ettiquette of giving donations to the church/priest?

Our Baptismal form for our boys states that donations are welcomed, we were guessing say $50-$100 per boy, but my MIL said more like $5-$10!!! I have no idea??? Do you give based upon your means? or by how much something means to you? Or what you think the Priest's time would be?

Also today we attended a viewing of a dvd about Baptism at the Church, two people left before us at the end, then as we were leaving we saw the last couple give the Priest some money, this had never even occurred to us, and i felt like perhaps we should have.

Is there a way to know when its appropriate to give money? i would have actually worried about offending by giving money as i'm not accustomed to this. And how do you know how much to give at certain times. For instance I am having my Confirmation at the Easter Vigil, would this be another occasion to make a large donation?

Also when do you give the money directly to the Priest? and are there times you give it in a box or such? and what do you say when you give it to the Priest? "Thanks, here you go"? (which sounds patronising) or do you say nothing?

Thanks in advance, it's a bit embarrassing being so naive about this but i have not been a practicing Catholic since i was a child.