I have just breed my first litter, so not the most experienced here by a million miles, but have just done it all, so fresh in my mind.
Worming with pancur should be from day 40 to 2 days post whelping. If you decide to worm the puppies with Panacur, it is at two weeks and 5 weeks. You won't need ot worm the puppies when born, as the wormer will come through in the bitches milk. I was going to do this, as I have almost a whole bottle left, which cost £26. However, the stud dog owner has told me today she has heard of a lot of problems after worming pups with panacur, and herself ended up with a sick pup on a drip after using it, so would never useit again. I guess people have problems with everything, but I am going to use Drontal puppy to worm my pups, which needs to be done at 2 weeks, then every two weeks after that until 3 months. It also is only one single dose, so not so much messing around.
Did your vet say 'at least two puppies' after a scan or palpation? Some people find scans accurate, some don't. I think it is less likely they are wrong with a small litter, but my friend had a bitch scanned, was told she wasn't in whelp, then a week later she had 15 puppies!

My own vet said it was hard to be accurate when scanning. I asked her to estimate the number of pups though, saying I wouldn't hold her to it. She said 7 or 8, but it could equally be 6 or 10. She had 9. She did start having clear discharge quite early, from about day 26, I seem to remember.