@Kirky658 I have 3 dogs and just going to wing it! We only got the third in October as didn't think we could have children and I wanted a forever baby (he is a 6 year old rescue but only 3kg)
Our other dogs took to
Him immediately because he was so small and no threat (more fool them) hoping they do the same with the baby to be honest.
Biggest change for them will be no more sleeping on our bed with us. We are
Moving from a Downstairs room to upstairs though so hope that helps them as we can do that sooner.
Things I've always heard is get things out in advance for them to get used to, so make basket, take pram on walks, playing baby crying sounds.
Work on the basics of no and leave and that will help with general obedience.
It is more than doable and he will be a bit older by the time baby comes.