Am I mad getting a puppy??

Here's the story.. My sons 5th birthday in 10weeks, our 18yr old cat had to be put to sleep 2months ago he was my sons best friend he's lost without having someone to cuddle and play with, so we agreed for his birthday we get him a border collie puppy this was before I found out I'm pregnant, was planned but didn't think il fall pregnant so quickly.. Now I'm wondering if it's a good idea to have a 6month old puppy when I've got a newborn aswell.. I don't have to work so I'm stay at home mum and my son starts full time school in sep so being home with the puppy to train it not the issue I'm hoping I can train the puppy while I'm pregnant just when the baby born will it be a struggle to spilt my time with my son a puppy and a baby.. Has anyone else manage this?? Or you think we should wait a little longer?? Any advice welcome..