I'd have a man to man talk before you even leave home.
Let him know that everyone is a rookie at some point, and that anyone can learn wilderness skills IF they keep a good attitude and ask questions, rather than let their ego get in the way.
Number #1 rule, NO WHINING
I'd also get him involved in the portage/map reading process right from the git-go. Let him feel he's a member of the team, and what he lacks in "skills", he can make up for in attitude and ASKING what he can do too help, rather than standing around WAITING too be told ;)