Told our son last night we were separating

Me (37f) and my husband (40m) have been om the rocks since April last year. We finally made the decision to seperate and told our teenage son last night. He was blindsided. My husband and I are still on friendly terms, we told him together but it was heartbreaking to see how much we hurt our son. We did our best to say that we both love him and will both always be there and that in no way did he was this about him. We have a therapist lined up for him if he needs it and he is allowed to ask anything he wants. It just hurts to see him absorb this huge change. The husband is looking at a house later this week and will move out in a month or so. Any tips for trying to keep the kid as happy and mentally steady? I just want him to be ok.