weaning 2.5dd off milk bottle

Weaning daughter off milk bottle.
i am in the process of toilet training and think her bedtime milk bottle is becoming an issue. She has one bottle when she wakes and one at naptime and bedtime. Sometimes another through the day if shes ill. I really would like to remove it as she sometimes goes through 3 a night so i know it isn't really a soothing object anymore.
also my son is 15 months and unsure if i should do him as well to save the pain and i feel it would be easier if i did both at once.
TIA