Here's my complicated situation. My wife is an author, and when her first book came out in January 2013, she, I and our two kids went on a 7 month book tour. This was an extreme but totally legitimate business trip: she did book signings in over 150 bookstores, dropped in to introduce herself in perhaps another 200 stores, visited book clubs, libraries, festivals, etc. to support her career (which, by the way, it really did).
My question is: how do I estimate the percentage of the trip and expense that was dedicated to business? Most of it was, but we did take some days here and there to rest and have a little fun. I don't argue that these should be deductible, but I'm not sure how to count them.
More tricky is that we also had the whole family on the trip. I legitimately function as my wife's manager, navigator, tour planner, etc., and so maybe my expenses are part of the trip. The children did add to the expense, and while they actually do help with the tour, I wouldn't try to argue that their expenses should be deductible too.
So how could I take an expense and indicate what percentage of that money is deductible? Is there any guidance from the IRS on this? Is there a worksheet where I could tell them that I think a $100 hotel bill would maybe have only been $70 without the kids, or that a $50 meal would only have been $30 without the kids, and pro-rate my deductions accordingly?
