I think they'll be just fine and if they're not, you'll know it over the weekend
If they're playing and cuddling all weekend long, there ya go
Luna was 3.5 months old when we got Izzy, who was about 6months old, and they got along from the first second. I think that when they're young like this, they adapt a lot more quickly than if your existing dog were to be say, older than a year or so. Just my limited experience
