Buying a puppy and moving date is prolonged, what do i do???

So we're moving and I've been dreaming of finally having a dog since I was a kid. We're renting currently and close in our house next month. I put a down payment and signed a contract for a puppy and the breeders agreed to keep the puppy a little longer until we were moved into our country home. Our landlord technically doesn't allow pets. I have family that would be more than happy to watch our puppy if needed. Problem is the home sellers need an extra week possibly two to move out so we can sign on schedule but due to them not having help moving until after signing day, they need more time. I don't want the puppy sellers to think I'm flaking on them or unreliable. I don't want to jeopardize losing this puppy at all. So my thoughts is do i just tell her and say we'll take her early like at 8 weeks like her siblings or do I wait for when we thought we'd be moved in and pretend everything went to plan? Please help.