Where do I start?

My sons parting gift from school 4 years ago was to find out he was going to be a dad! He didn’t know the girl and is testament to the fact it only takes once. Fast forward 3.5 years and our adorable GD who has lived with us since she was born with our son is wonderful. It certainly wasn’t part of our plan to be essentially parenting again in our 50’s but despite the challenges she has filled our life with joy. Our GD’s mother is not really involved and has an extremely chaotic lifestyle which unfortunately seems to be getting worse and we imagine will at some point drop out of our lives completely. Our sons early life journey was not what was planned even by himself but he’s been trying as best he can and has fortunately working since he left school. Earlier this year, a new young lady arrived on the scene and quickly became a big part of his life, my husband and I could spot some early signs from her of ‘wanting’ to be a mother despite having just completed one year of college. We warned our son to be careful and consider the consequences as he is still so young. At the same time, he is struggling with some mental health issues which are probably associated with becoming a parent too quickly. He is receiving help for this. 24 hours ago our worst fear was confirmed when he told us quietly that his partner of 7 months (18 years old) is indeed pregnant albeit very early on. My husband and I are totally numb about this and have no idea even what to say or feel! They have no real means to be independent, council lists are so long for homes, she doesn’t work and neither are emotionally equipped. As a side, the girlfriends mother (who was young when she had her) has a 3 month old a 2 year old and a new husband which is why this young lady came to stay with us as she felt pushed out. My husband takes early retirement in just over 2 years and it was our plan to downsize and travel.. our 3 year old sees us as very much her parents, which we don’t mind at all and have embraced but where on earth does this new pregnancy leave us??? We feel let down again that we haven’t had the ‘joy’ of becoming grandparents but are left anxious and disappointed yet again. We can’t change things but where on earth do we go from here to ensure all are protected and safe. As a side, I have 2 companies that I run and my husband holds a very senior role in the public sector. You couldn’t actually make this up...