My plan works as follows. I hope this gives you some ideas. My daughter is 9 years old. Since she is of school age, my ex wife and I trade off only every two weeks or sometimes every other month. That way she is not too stressed about schoolwork. With my son, me and my ex gf trade off every other week. He is only 2 years old and he can handle all of the moving around. If he were in school we would do similar to what me and my ex wife do. But to answer your question, the best answer I can give you is to sit down and talk. Be civil towards one another, I know it's hard but it's the only way you will come to an agreement with your child. If a proper agreement cannot be reached, then I suggest that you seek legal advice.
Relax!! Word of advice, do not hire a public defender for a DWI / DUI case. A good attorney will charge anywhere from 3-5K to take a DWI case. Don't be scared though, chances are you will get a PBJ. I have attached a really good site targetlaw.com to search for DWI attorneys. I would do a search for Maryland DWI attorney or Maryland drunk driving attorney or Columbia DWI attorney and so forth. Just do a search and start calling around to the listed lawyers. You can also check out a site called findlaw for more information about the DWI in your state. Again, don't worry you should be fine.