J.A.
Thanks for asking this question! I am in the EXACT same situation with my husband on spring break this week. We have a baby due right at my son's 2nd birthday so we were thinking of convincing him to give it to the baby, but I don't know either.
He has recently started to call himself a big boy and correct people when they call him a baby, so maybe we can work with that! Everyone's suggestions below are similar to those that I got a couple months ago when we were thinking of doing this over winter break.
I have heard that you can 'train' any child to do just about anything in less than a week so if you have the time and patience- I say go for it!