That's predicated on the false assumption that everyone finds kids important. Many certainly do not, like myself. I'd rather have more money and time than raise a child.
As someone with a kid, this seems like a very bad reason to have kids.
At my funeral, since I will be dead, the only ones who will (presumably) be suffering at that point will be the mourners, so arguably, the less people at one’s funeral, the less overall suffering there is.
Funeral's don't have to be about suffering - Death isn't the end of the story for many people of faith. Leaving a legacy to the next generation is quite possibly the most meaningful thing we are capable of doing, no?
In terms of the lens of the Regret Minimization Framework (for me) I would regret not having the family I'm leaving my legacy to at my funeral.
I just said it doesn't matter, because I'm dead. But if I'm going to answer your question, friends and family would be there, just like everyone else's funeral. Even if I don't have kids, I will have other friends and family who do.