On the other hand, "hitting him" with something shorter he's more likely to actually read may be more effective. Tom's book is brilliant if someone actually opens it, but it is an intimidating size, and when something is presenting a view you disagree with AND is enormous AND you're busy (as Ken Ham no doubt is) you're less likely to open it at all. Could start with "Why do you believe that", which is also great, but then lacks the depth of Tom's book. Really hard to know what would be best.
Before anyone does this, check with Tom whether he's already sent a copy to Ken Ham. He posted a while back that he was intending to send copies to prominent people, asked for suggestions, and I suggested Ken Ham, no idea if he did that.