Newbie, we certainly understand the frustration. Like walking into the world's biggest candy store and being told you can have anything you like...as long as it fits in this thimble. Or like putting training wheels on a Harley FatBoy. lol.. I can just hear you now: "Aww, man this sucks!" But would you rather walk out of the candy store having not tried even that thimbleful? First encounters need to be somewhat brief and limited; it limits the number of ways we can hurt each other as two completely unique individuals explore a completely foreign concept. Neither of you knows how you (or, more scary, the other) will react "under fire". Setting rules and sticking by them is important in setting the stage. When your first encounter happens, what you wife will be watching for is just how closely you listened to her, and how much you respect respect her fears and feelings. Yeah, I know you respect her, but she's going to want to know just where her feelings lie on your priority scale. If you let the little head think for you (and believe me, he'll be at his most persuasive), he'll tell you that your sexual satisfaction is more important than some stupid rule that just doesn't make sense anyway! What I'm saying here is, while you might personally think the rule is stupid, why you are still going to follow it is not!
Sit down again with your wife and tell her that, while you will still respect any boundary she imposes, you'd like to understand why this act or that act is so uncomfortable for her? You might be even more surprised at her reasons. But don't try to persuade her to drop a boudary. Err on the side of caution and play conservatively. There are likely some boundaries that are going to be absolute for her, but also some that are more of a grey area. Find out what those are. Is it kissing? Oral sex? No touching/caressing the face? No eye contact? Another thing you could also try is setting up a signal system (kinda like baseball) while you're in the middle of things. If either one of you changes your mind about something, you can signal the other "No, don't do that (even if I said it was ok before)." or "Yes, go ahead and try that." Just don't make the signal thing too complex or a) you'll forget the signals, or b) your partners will wonder if you rolled in a patch of poison ivy with all the nose-scratching and ear-tugging etc.
Well, we hope your first play encounter is fun and relaxed. Don't let the idea of what you can't do interfere with the fun of what you can. Just remember to remember each other's feelings while you're experiencing your own and you'll be all right. Please keep us updated about your first encounter, too! We're all interested to see how things went