It's not ideal but if you let the camp know that you won't have two deep leadership during the day on Wednesday they can provide someone.

I figured out that the best way to handle scout camp is to bite the bullet and take the whole week off work. The benefits are many.

1) Continuity in leadership makes the camp go a lot more smoothly. You know what all of the boys are doing and things don't drop off passing from one leader to another.
2) You tell the scout committee and the parents that you are one leader for the entire week. They need to step up and provide a second leader.
3) Fewer volunteers means fewer flakes to back out. If you have 1/2 the required leadership covered, you probably only need 2 or 3 other leaders to cover the other half. Make sure those ones are solid. If you are in a situation where you are relying on 5 or 6 people to cover the week, odds are good that you will have a hole or two.
4) Less stress. You don't have to worry about what's happening while you aren't there. I had a year where I split the week with an assistant. When I showed up the group was disorganized and the boys were so far behind on their work. The week wasn't nearly as productive as it should have been.