First of all, Golden Retrievers are lots of fun just being themselves. I think the most fun you could possibly have is training them to do things and then later on giving them the commands to do the tricks. I love to show off my dog Liz (Lizie) and her smartness to other people. It is fun for both of us, I get the pride and she gets the treats. Besides that, I like playing fun games with her, fetch is a common one that almost every dog loves, try doggie soccer where you both kick and push around an empty plastic bottle with marbles or stones inside, or tie the bottle around your leg with a rope and run around with your dog chasing it down. As far as for outdoor activities, dogs love dog parks where they can socialize with other dogs. Go for a jog with your dog in a new place like the beach or take them to a kids playground in off hours and have them swing or use the slides, ooh that one is a lot of fun. Try hiking, my Golden Retreiver loves it. Water parks are fun also (though summer is comming to an end) for some of us.