You have done a great job, and now a new phase of life is opening up for all of you. It is tough I know, but life moves on, and, just like when our children leave home and set up on their own for the first time, we have to pat ourselves on the back for a job well done that has enabled them to make their own way in the world.
How wonderful for your DD that you were there when they needed you.
We had our DD, SIL and GS with us for 9 months when their house had a fire and there was a lot of clearing up going on - we did surely miss them when they went, but there were compensations too and it was good to see them getting back on their feet.
A new situation awaits you all with the forging of changed relationships and new ways of working. But that little lad will be rushing for a cuddle when you see him, and yours will always be his second home, where he feels secure and loved - what a wonderful asset for him!