I mean .... you're not obliged to share anything about what happens within your marriage. People hide or just keep their own counsel on good/poor financial situations, marital problems, the fact they're trying for kids, what they did on vacation and an abundance of other things; it's not weird at least within my cultural background. Indeed it's kind of nice to be able to celebrate personal successes as a couple or with a small, supportive group rather than needing to tell the world. Seems like you must have a handful of people in your life who both would be supportive or interested and that you aren't mistrustful of. I have coworkers who I discuss investing and financial independence with because they're into it. Some people just aren't and that's okay.
I tend to believe that whole "people are thinking of us much less than we think they are" thing anyway, and it's unlikely anyone actually cares why we go to the office and such to be honest, don't overestimate this stuff. My mortgage will be paid off super early too but nobody has ever in my life asked me where I am in terms of getting it done. People have their own stuff to concentrate on.
On issues with picking up bills - you're going to have to bring it up, directly and ideally when you're together at a non monetary event. If you've allowed the situation to develop where you're picking it up all the time that's kinda on you too, so some sort of gotcha where you ask for it to be split after everyone has eaten is a little off in my opinion. The comments assuming your family are ungrateful money grubbers are sort of comically unfair given a couple of paragraphs of info, seems just as likely that it would be a very awkward but ultimately okay conversation.