Turning on iMessage on iPad after its been disabled for a while

So, this sounds awful already but, I need to check my husband's messages on his iPad while he's at work. I suspect he's using pills, but I need to confirm 100% so I can get him some help. Anyway, he's had his messages on his iPad turned off since the middle of December. if I turn them back on what will happen? I know he gets a notification but I know his e-mail so I can delete that message before he ever sees it, but what will his messages look like after, will it update with all the new ones? And there's no way to go back and get rid of those I'm assuming?

Thanks in advanced,

A very concerned wife