I think now is as good a time as any. One trainer whose on-line stuff I have come across - I forget which one, I listen to loads of dog stuff - says that socialisation is really about exposure. It's not about running up to greet people, it's about seeing pushchairs and wheelchairs and men in funny hats and kids playing football and women in specs - just getting the dog used to all the different sorts of human. And it's not about frolicking about around unknown dogs, either, it's about seeing lots of them, never being harmed by them, learning to stay near to you unless you allow some interaction. In other words, seeing chihuahuas and Labs and spaniels and terriers and whatever other dogs your area can provide, to get used to every sort of canine.
You can also think of this as a time to build resilience, by getting your puppy used to all sorts of noises (screeching children, crashing pans, the washing machine, pressure washing the patio, chugging lorries, trains, whatever) by starting the noises off fairly quietly and then gradually ramping them up. Building resilience also includes teaching the pup to be left alone for short and not distressing spells and then lengthening them, getting it used to all sorts of surfaces and locations - sand, wooden footbridges, whatever you are likely to encounter.
About the only thing you can't provide at the moment is controlled interaction with known 'safe' adult dogs, and crowds. But we have no idea where we will be five weeks time when you bring your puppy home, or five weeks after that.
Cats: dunno about collies (never owned or lived with one) but I have two high-drive, prey-driven, field-bred dogs in the house and the cat is in charge.
Your OH: He is a pessimist (he says realist) I've got one of those. He is usually putty in the dogs' paws. It is actually pathetic.
Higher drive collies especially have a very predatory stance about them and other dogs don’t like it.
This is very true. My older dog was stalked and given eye by a collie and after brassing it out for a bit (about 5 seconds), he ran off crying into the bushes...
Good luck with it, OP. Check out the breeder to make sure you're happy, teach your DC to do right by the dog, and have years of great companionship.