As you are in the planning stage ask your vet practice if they dock if so then get them done cos after the pups are a few days old it will be to late,Yes nowt wrong with a spaniel with a full tail work wise but you will run the risk of a damaged tail every time they are worked . you are stacking the odds against you for selling the pups to working homes as some won't have a worker in the kennel that has a full tail.O.M.O.mind good luck.