Hmmm where is your a guest so enjoy the party? if she does not have a DOC I think it would be a good idea to distribute the responsabilities between more people other than yourself. Can her mom or another relative take care of at least half?
what about her bridesmaids?
Yes, ditto everyone else. I think it's great that she is already so organized - that list will definitely come in handy! Some of the bigger jobs - like pictures, cutting the cake, etc. - will certainly require more than one person,
You may ask her when she will have access to the venue. If she has it all day or even the day before, that would help a lot with some items that can be done ahead of time.
If she has a DOC, she might just want someone to follow up/make sure things are done to her liking since, as the bride, she will be preoccupied that day. In that case, you could just sort of go down the list and check on things for her shortly
before the wedding starts. If she doesn't have a DOC, I think I would ask her to let the BMs or family members know that you will be heading up the prep, but need all hands on deck to help!
Good luck! You are a great FSIL to help with all of this! It would be hard for me to turn someone down, as well...despite all the work :-)