This issue is one in which I would be shocked if there were not a multitude of approaches and results. However, I think that the best advice that I could give be would be a set of caveats that may or not work for you:
1) Your parents will respect you when they see that you are dedicated and sincere and that Torah Judaism is your way of life, as opposed to a cult. If your parents become frum with you, that is fantastic. On the other hand, if they don’t reach that level, you have to work for their tolerance of the fact that you and your family will be living a different way of life than themselves and your siblings and still maintain a relationship with them, even if it appears that they barely tolerate your lifestyle and possibly overlook conduct by your siblings that a Torah Jew would not approve of in any manner. There are some issues such as attire,education, kashrus, Shabbos and views on Tznius, etc. that should be avoided unless you have the unusual knack to present a positive approach. Sometimes, your children will be better able to express themselves on these issues than you because you may be overly emotionally imvolved in dealing with your parents. Here’s an example. A family relative once asked me how I could be sure that our kids would marrry Jewish spouses. I turned to our kids and they both stated that they believed that their education both in and out of school had shown them the positive beauty of Shabbos, Yom Tov, Kashrus and a life based upon Torah. Marrying a non-Jew would be a complete negation of their roles. They can more readily explain the fact that they don’t go out with the opposite gender a lot more quietly and positively than you can in a variety of ways.
2) I think that discussions with your parents should avoid comparing Torah Judaism with heterodox (Conservative, Reform, etc..) Jewish movements unless they bring up the subject in a direct way. These discussions can deteriorate into a rant about who is more tolrerant or intolerant, a classically unproductive conversation.
3) Obviously, invite your parents to significant events and milestones in your family’s life and education- Chumash party, graduation, Bar/Bar Mitzvahs, weddings, community functions if you are an honoree . Most parents, even if they engage in some Ortho-bashing, shep nachas from such functions.
4) Kashrus, Shabbos and attending family simchos that are in heterodox venues , etc are halachic issues that can be dealt with a competent rav who knows not only Shulchan Aruch, but its fifth and unwritten component-common sense.
I think this would all be easier on my non-observant ILs if my DH had announced he’s gay rather than keeping kosher, observing Shabbat, etc.!!!
For one, that would have meant *I* was not in the picture, and I am much reviled these days as “the one who started all this.” grr…
but its fifth and unwritten component-common sense. This is so true, common sense is a valuable tool not used enough in interpersonal affairs. That’s sound advice.