WagginTail you have recieved some good advice, just for amplifiction let me throw out these suggestions.
1. Keep your recovery your number one priority, you put one single thing ahead of your sobriety and it may very well be the second thing you lose after you lose your sobriety.
2. Get a lawyer and follow his advise, I would suggest you find a lawyer that is in AA, there are far more then you can imagine, ask him for a referal to a lawyer who has dealt with these types of matters before.
Congrats on the 5 months of sobriety, keep doing what you have been doing, ask your sponsor if he can refer you either to a lawyer or to some one who has been through a divorce involving child custody that may be able to give you a lead on a good lawyer.
Please do not gamble on trying to do this your self.
One very important thing to keep in mind just in case the custody of your children does not go the way you hope it will................... DO NOT DRINK OVER IT!!!!!!!!
Child custody can be taken back to court any time and many times, if you do lose custody due to your drinking in the past, you can go back to court and show that you have been sober even though you lost custody due to your past.
One other very important thing to keep in mind is the courts do not automatically give full custody to the mother like they did in the past, they either give joint custody to both parents or they give custody to the better parent.
The fact that you have been the primary care giver for your children for years speaks volumes in your favor! One thing I am sure your lawyer will tell you is to remain flexable in regards to custody, do not turn down joint custody if it is offered.
If you get joint custody keep meticulous records of every time your wife ask you to keep the kids during times she should have them, keep records of when she brings them home late or picks them up late.
Make sure you pick the kids up on time and return them on time. Remember that she will always be their mother no matter what and you will always be thier dad.
Do not use the children as weapons and for the sake of your children DO NOT bad mouth thier mother!!!
I was very lucky when my first wife and I divorced, I was granted primary care giver and my ex paid child support! Now here is the greatest thing for the kids, I never bad mouthed my EX to them and she never bad mouthed me to them!