Husband going out to a bachelor party/bar hoping

Ok so I'm kinda of upset that my husband wants to go with one of his friends brothers n cousins. They said that they are going paint balling and then bar hoping. One of his friends brother is getting married. He had already told me that he was probably not going because he was going to have his son, (from another relationship) and plus he don't have money to be spending like that and that it was going to be expensive. So today he calls me on his break and tells me that he told his friend that he wasn't going because he had no money, and the friend told him not to worry that he was paying for him. The issue with this is that I don't like him going out with them because they do drugs (cocaine) n my husband used to do them also I'm just afraid that if he goes, he's going to do them again n he gets super waisted n everything goes down the drain. So I'm like really your going n your going to leave me your son while you go out, and he already told me what I was going to do while he was out. He told me that my mother in law was going to be at his aunts house because she wanted to see the kids. I rarely get Saturday's off and I thought we were going to do something together. That's why I was so upset. Am I being upset for nothing or overreacting over this. Ugh