Changing a babies last name

So my partner doesn’t like his family and doesn’t speak to them

We gave our babies his last name but I’m debating on saying we should change it

I’ve brought it up and he says the only reason he doesn’t really want to is because it costs money but if it was free then he would go for it

We are much closer to my family and have debated on even just changing all our last names to something we enjoy and starting our only family line/last name

What would you guys do if you’re not close to their family?

Would you have your whole family take your last name? Create a new one?

We are not close to his family for lots of reasons and some relate to survivorship of different things