Should I let my husband go on a one-day trip or no?

We live in Texas and have been together for 3 years and have never gone on trips by ourselves. My husband's sister is a musician in NYC and has a very important concert in a week. My husband wants to go to support her because she has no family in this country except him. She says she would really love for him to be there for her. My concern is that I have been given very short notice and I can't take that day off from work. I believe I should have been given more notice, but my husband said the concert was not approved until a couple of weeks ago. We are doing well financially but it is also my concern that air fare and hotel add up to a nice amount when they are booked the week before. Bottom line, is it a good idea for him go by himself or not?