My mom & stepdad graciously offered to cover the entire cost of the wedding for FI and I. My father & stepmother pleasantly surprised us all by saying that they, too, would contribute. I do not know how much they will be contributing, as it's not my place to be involved in the money side of things (IMO).
That all said, we're not splurging on an extravagent wedding. We have an overall budget of about $20,000 for 175ish people (mostly family).
My aunt has offered to my parents to cover the cost of the photographer as her wedding present to FI and me. My mom filled her in on the option we'd picked out (which is on special - YAY!!!, but is still about $1,000). I, of course, have already verbally thanked my aunt for the offer.
When is it appropriate to give her a written thank you? When the photographer is paid for (in part or in full)? At the rehearsal dinner? At the wedding?
Our wedding is in August 2012, so I know things are getting done well in advance. I'm just not sure what the ettiquette is for such a gift.