S.,
If you were my friend, asking me this out at a cafe, I would probably tell you "I don't know" because there are several facets of your post that *you* need to be 100% solid on before you make this decision.
1. Your familial relationships with your dad and your business relationships with he and your husband-- these are huge considerations. Is your father going to feel that you are leaving them in a tough spot; are your shoes hard to fill and will training someone to do what you do be a hardship on the business? Will they absorb some of your work and shuttle off the less-important tasks to workers? What would this transition look like, ideally, because it's good to already have a plan in hand to take back to dad...
2. Once again, the familial relationship with dad. Is this going to be a huge problem for the two of you? Is this going to trigger some old, bad stuff that's been at rest since the two of you were working together? You need to figure out what your father/daughter relationship is going to need. Do you need to strengthen yourself so that you don't feel totally guilty and horrible about leaving the business?
3. Is this a temporary or permanent leave? People need to know so that they can move forward. Do you want time to get things back to a more functional way of living, or are you just *done* with the work? Sometimes we can get these two ideas confused...
4. What will you do/feel if the time at home(without work) doesn't relieve your feeling of being overwhelmed? Do you have indications that your son's anxiety/ADHD will be improved because you are more hands-on, or is this guilt on your end? (Please forgive me for asking that last question-- I really don't know... I do know, however, that guilt is sometimes the worst reason to make a decision.)
It's so difficult to make a decision that is good for *everyone*. If it were me, I might go back and visit with a counselor a couple times to talk it through before even mentioning this to anyone. That's also what I would probably advise a friend. You can ask this question, and we can all chime in, but you and yours are the people who have to live with this decision, not me.
If you do decide to be a 'work in home' mom, (that's how I perceive my job), my best advice is to give yourself some activities and goals and keep a fairly routine way of life for everyone's benefit. I need routines to my day, or it would be too easy to get distracted. (Which reminds me, time to take a shower now!) If you are solely focused on the kids, you'll get burnt out more quickly, so find ways to still get sitters/help from time to time so you can get time out for yourself and do things to feed *you*.
Good luck on your decision and let us know how it goes....