Good you took action on the lawyer consultation! It doesn't mean you have to take action, but having the knowledge will empower you and inform your decisions. Also, don't be afraid to meet with 2-3 to make sure you're comfortable.
In terms of the D, here are the major areas:
Child Custody - With your biological kids being 17 & 19 this will be less of an issue for them, but I assume adopted children are the same under the law as biological? Talk to L about that.
Child Support - Again, due to their ages your biological kids won't be a major issue but check on your adopted child. At 4yo it could be a long time (until 18yo, or 21yo in some states).
Spousal Support - Often states have calculators based on length of marriage and disparity of income. Finding a calculator or your L should be able to give you a good idea.
Assets - In the US states are either Equal or Equitable Distribution. Equal meaning divide everything (assets AND debts) in half, equitable meaning take your premarital assets off the table and then divide everything in half. I'm guessing because of the "high school sweetheart" status neither of you had many premarital assets.
I'd definitely talk to L about what actually makes the financial split official. If she's running up credit card bills spending on clothes, makeup, OM dinners and hotels...whatever, can you just section off accounts now or do you need to make a legal filing to cut off her debt from being on you.
