Foster son scared to go out of town

My cousin passed away last week and her funeral is next Saturday. We have to go to Arizona for it. We will be staying at my great aunt's house. Our 15 year old foster son will be sharing a room with the boys there. He still has trouble talking so he wrote us a note a put it under our door. We found out from his caseworker why he tried to burn his last foster families house down. It was because the mom starved him and the other foster biys and foster father sexually abused him. When they sodomized him in the basement he snapped... I believe that has to do with why he wets his bed. In his note he said he's scared to be in a room with the boys. He's nerbous about wearing goodnite pull ups there theres and is afraid the boys will hurt him... Me and my husband are trying to find a solution. I was wondering if you guys had one. Also should we respond also in a note or just talk to him face to face?

I thought about him sharing a room with us but we would be breaking rules. Foster parents aren't supposed to share a room with the child. Idk uf it's the same in other states... But ig breaking this one rule couldn't hurt. It's not like he will be in the bed with us.