Mr and Mrs Key and their children Stephanie and Max will arrive at Balmoral Castle on Friday afternoon ahead of afternoon tea, which Mr Key said was "compulsory for all the guests at 5 o'clock".
They will attend two dinners during their two-night stay - one a black tie dinner, and the other a more casual barbecue.
"Then you've got the whole day on the estate on Saturday and there's a range of activities, from horse riding to shooting to walking to golf," he said.
"And Sunday we will be going to church with the Queen and then back for lunch. So there's a variety of different meals and activities - no jeans on the property."
Mr Key said the visit would include a royal audience with the Queen.
"That will be an opportunity to just update her about what's happening in New Zealand, as I always do when I go to London, but normally that's at Buckingham Palace or Windsor Castle."
Mr Key also discussed New Zealand's bid to become a member of the UN Security Council, saying the country put itself forward every 20 years or so.
He said being on the council would give New Zealand an insight into what was happening in the world.
"Secondly, you can make a difference. Last time we were on, we made a significant difference for the people of Rwanda."
Mr Key said New Zealand had a contribution to make as a small country with an independent foreign policy, and is often seen as an "honest broker".
