Wife characterless. Can i get custody of children if i file a divorce?

What your wife has done comes under the ambit of Adultery, which during the subsistence of a marriage is a ground for getting a Divorce decree. Further, adultery by the spouse itself also amounts to cruelty and cruelty is also a ground for getting a Divorce under the Hindu Marriage Act 1955. 

Remember it is always advisable to implead the adulterer along with the spouse to contest the divorce case as it will provide social and moral pressure on the spouse to come to terms to give divorce decree. 

In respect of the custody case, your elder daughter has crossed the age of 5 years and at that age generally children have developed cognitive traits, wherein the court will elicit from the child about her choice that with whom she would like to stay. The children's interest will be the paramount consideration before the court for giving custody to the one parent against the other parent.  Also, the non-custodial parent will definitely get visitation rights. 

It may please be noted that for getting permanent custody of the children, the interested parent has to file a custody case, and contest it on various grounds as applicable. You may contest the same stating the impact your children can have due to the wayward behavior of your wife, and once the court is convinced that giving your wife the custody of your daughters would not be in the best interest and welfare of the children, you may be granted their custody accordingly.