I think there are two possible scenarios to prepare for -- the benign visit and the worst case scenario.
I would suggest trying to keep things on the benign "shepherding" level as much as possible:
1. Your wife has been in the hospital a couple of times and you have two young children to care for and job responsibilities. There have been some tough times and a lot of stress on both of you that have demanded your attention, but the two of you are working through it together.
2. You appreciate their concern.
3. If they would like to share scriptures with you, you would appreciate hearing about Jesus' ministry as the fine shepherd, Jehovah's lovingkindness in the midst of our difficulties, etc.
Since you're not ready to DA or get DFd at this point, don't discuss doubts or criticism of the organization unless they or your wife force the conversation in that direction.
Let's consider the worst case scenario -- your wife outs you as an apostate, shows them printouts of some of your email correspondence with me, and they start questioning you about your faith in the organization.
One option, of course, if that actually happens would be to cut the cord, to tell them you don't believe it's God's organization any more, that you're convinced it's a cult, etc. It sounds like you've decided that for the sake of your wife and your marriage, you want to avoid this route, at least for now.
Another option, then, if you're outed, would be to tell them that you aren't trying to cause trouble at the KH or create any dissension amongst the brothers or sisters. Ask them if they feel you have done that in any way. Most likely they will say no. You can nod and look like that settles it.
If they press you and you decide you need to answer specifics, you can tell them that in the midst of all the stresses you and your wife have been under you are being stumbled somewhat by difficulties you are having trying to understand various things the Society teaches about the 1914 generation that seem different that what you were taught over the years. You can also tell them that you understand where the WTS gets the 1914 date but that you don't understand how they have come up with the 1919 date from the Bible. You might add again that that you have been careful not to raise these issues or stumble anyone at the KH, that you're trying to work through things yourself. You can tell them that you're not challenging them to do anything or prove anything, that you're only discussing this because they brought it up by asking you the question.
That seems to me the best way for you to be truthful and avoid a JC without groveling.
But let's face it -- if your wife wants to out you, she's got enough hard evidence to nail you. Likewise, if the elders want to DF you, they'll be able to do it.
If that does happen, so be it. It's out of your control.
As messy as that would be, in some ways it would be better than more of these repeated cycles you've gone through in the last year where things seem to settle down and then your wife gets all upset over something, calls you a filthy apostate, and threatens to leave you and out you to the elders. If she thinks you're afraid of that, she'll do it again and again whenever she feels the need to be empowered.
The real problem, as you noted, is that your wife won't question the organization. If you're really lucky, the elders will say or do something at this meeting that will cause her to doubt the borg and you can come to her defense.