I recently heard from a couple with several children, one of whom has ADHD. The husband also has ADHD and is struggling to get his symptoms under control. He rarely follows up on what he promises to do, which is driving his wife crazy. She is responding with typical parent/child dynamics - taking over everything he isn't doing, and getting on his case about his failures in angry and belittling ways. In this context, the husband asked the question "Should we tell our kids about my ADHD? My wife is concerned that she is always coming across as the bad guy, rather than me." Hold up there! Let's discuss both the question and the answer!
First, let's discuss the idea of 'bad guy' as put forward in this question! Before I do this let me remind everyone that I totally and completely understand how hard it is to live with unmanaged ADHD symptoms. But the reality is that if the wife is harassing and belittling her husband all the time (no matter WHAT the reason) then she deserves the label 'bad guy.' She is choosing to behave in a certain (negative) way. No one is forcing her to deal with her frustration by taking it out on everyone. Yes, her frustrations are real, but that doesn't get her off the hook for her particular response...no matter how understandable that response is. The unspoken part about her complaint about always being the bad guy is that she not like the role and she doesn't like herself when she's in it. The only way to change that is to not choose to be in it.
You (and she) might respond by saying 'wait a minute! She isn't choosing to have the ADHD symptoms around that keep him from doing what he commits to!' That's true, but she is, nonetheless, choosing her particular response. Other options would include: asking her partner to get a coach in order to create new habits; hiring out some of the responsibilities if they can afford it; calmly explaining how important it is that he seek medical treatment and behavioral therapy; letting go of some of the less important tasks (lessening her own burden, as well has his); refusing to take on the tasks he doesn't complete; giving him only the tasks that impact him so others in the family feel his disorganization less.
And, is the ADHD husband a 'bad guy'...or just someone struggling significantly with a particular disability? To make up an example for illustration, if he had no legs and couldn't make it up the stairs to make the bed, is the outcome any different from his having significant executive function problems that interfere with his ability to organize himself and make the bed? Either way the end result is the same - the bed doesn't get made. But our ability to "see" the missing legs (and imagine the enormity of the task) helps us be empathetic, while the inability to "see" how hard it is to organize a brain impacted by ADHD (and the relative 'simplicity' of making a bed for those without ADHD) leads more readily to resentment and anger. To take the analogy one step further, both the legless partner and the ADHD partner need "systems" in order to participate fully. For the former it would likely be living in a one-story house or having an elevator, perhaps using a particular type of comforter that is easy to manipulate, etc. For the ADHD partner the system might include an audible alarm, a white board in the kitchen, memory training, medication to improve focus, and more.
Moving on to the second part of the question - should we tell the kids? Yes. It's hard to understand why a person with ADHD responds the way they do if you don't know about the ADHD. Kids are just as likely to misinterpret distraction as "my Dad doesn't care about me" as a wife is to think her partner doesn't care. Not only that, kids benefit from seeing that not everything comes easily - that it's okay to have an issue that you struggle with, and to put hard effort into making an improvement in your life. Though it often wasn't pretty, my children did eventually benefit from seeing that the hard work my husband and I put into our relationship actually paid off...and that BOTH of us had to do the work. Furthermore, the child with ADHD in this family will benefit tremendously from understanding he/she isn't alone in struggling with ADHD...even Dad struggles! They can work together on learning how to use a calendar or alarm to meet their reminder needs, for example, and both enjoy the experience just a bit more because they are doing it together.
I found myself asking (out loud) the very question posed by this couple just the other day. "Why do I always have to be the bad guy?" is what I asked my husband. He didn't respond...and didn't need to. This is a conversation we've had before. His view is that I care more deeply about the details of how things work in our household (read: I want to control things more). If I'm the one who cares, then I'm the one who needs to express that I care...and also 'suffer' any consequences that accrue from that. What I've learned over many years is that there are often (but not always) many different ways to do things - including the 'not doing/saying anything' way. Many times, though it's hard for me to personally pull off, not doing/saying anything turns out to be a really good approach. When I don't interfere, kids feel they have more control and power...husbands feel they are appreciated more...I feel less resentful...
There are some things that MUST be said (like "are you using birth control?" and "don't stick your finger into that light socket.") But there are many more things that really can be let go than I used to realize...and perhaps than you realize, too.
So, yes, tell the kids and have open discussions about what it means to live with ADHD and how ADHD is managed. Move away from parent/child dynamics. And understand that it is your own actions, not the situation in which you find yourself, that defines whether or not you are a "bad guy."