Is your current gundog okay with other dogs?
Unless the older one has any real issues they usually accept pups with no problems ... easier than bringing in a new older dog. They usually realise more or less straight away that pup is no threat and they are top dog. Pups are usually well tolerated and treated differently at least until a few months old.
Is the older one a lab? Our Flatties and labs have always been great with pups. Our lab pup is about 8 mnths old and older dog still lets her take food out of his mouth and so on.
I would introduce them at home, indoors. Big one won't be running around that way and trample pup before he has worked out what the little bundle is. Our pup sleeps in a crate in the same room as the older dog. Crate means that she wasn't trampled underfoot as Flattie greeted us in the mornings. Accidental trampling

was our biggest concern.
Have fun