Someone's a little envious that they don't have kids yet.
Yes, this comic is a little late because despite being "my" day, it was still a busy one getting the house ready for company. And as much as I might have wanted to relax, that wasn't going to happen for the whole of the day -- and definitely not long enough for this to appear.
Which is probably a good thing, because this strip was originally so much more complicated in my head, and yet boiled down to the same thing.
I'm sure "Dad" ("Grandpa") will appear again soon.