[He's used to bluntness, so it doesn't bother him. He does shift awkwardly on his feet a moment though, before actually responding.]

Although it won't be an issue tonight, I wanted to give you advance notice that I won't be available to watch the equipment tomorrow night.

[A pause.]

Unless you can't find anyone else, anyway.

[He knows she has other volunteers but he doesn't want to leave her with no one if they're not an option for whatever reason.]