How to be there for my bonus son and daughter TW

My bonus son(15) and daughter(12) have been through a lot these past few months. We not too long ago found out they were being molested by their step dad. According to them their mom had no idea and they were told not to tell her. They usually come down to see us for the summer. Their mom sadly died March 28th. She accidentally overdosed on pain medication she got from a friend. We wanted to get down there for the kids but we have no vehicle and their step dad told my husband it was okay and he would keep the kids here until they finished the school year and then drive them to our state. That was the agreement and I know my husband feels extremely guilty. If he would have known what was going on, he would have found a way to get to them. And then we could stopped what happened from happening. Their step dad was molesting on my bonus daughter and my bonus son tried to protect his little sister so their step dad raped him.... My bonus daughter said she heard him screaming in pain and she got the house phone and hid in the cabinet to call 911. Thats how we found out about EVERYTHING! My husband paid a friend to let us borrow their car. My bonus son ended up having to get stitches. It was awful. Step dad is in jail and kids are with us. We are trying to get them into therapy, but the wait list is kind of long. I want to be there for them. We were never really close but I want them to feel safe. Especially my bonus son... When he's in the bathroom I can hear him in pain while trying to use it. These poor kids have been through so much. My husband is taking my bonus son back to the doctor Thursday to make sure what happened didn't cause even more internal damage because he will sometimes wet his pants. Not everyday but at least once a week. My bonus daughter wants to stay by her brothers side. They have there own rooms but almost every night she crawls into bed with him. This is all so heartbreaking...