Is he clean? What did he do to get that way? Are they close? He might be an option. Think about it... You don't have to get him involved this instant.
How much do you want to shake things up? Cruising around in a car drinking is not something most moms do. We tend to be helicopter parents wrapping everyone and everything in bubble wrap... This sort of behavior indicates how far her mind is. It working sadly.
Stay truthful with her that you see her drinking and it is a serious problem that needs to be addressed for your kids, your relationship, who she could impact in a car accident. I'd express the situation factually.
Maybe your first change is you no longer drink heavily? Can you stop? You by default get to be the sane parent. You need to be ready to drive her home, drive the kids around, assume she's already been drinking if you head off somewhere.
She is functional. She could be this way for years, so you want to minimize the risk of driving as much as possible... And I'd be honest about it. I am concerned about you. I. Love you. I'd hate to see you suffer the consequences of hurting someone. So I will drive.
Keep your eyes open. Sadly people are right when they say, more will be revealed.