Printing out the photos will cost you money. If you want to show people, you may just want to bring your laptop with you. Though, the bright sun will make that difficult. I just don't think selling at the dog parks is going to be much of a money maker.

I *would* bring a laptop to your portrait sittings and proof on site. I get 95% of my orders that way. Those people have come looking to BUY photos. They have the expectation to buy photos and getting them while they are hot, helps

Oh, and your album that says "greyhound", those are whippets. Greyhounds are much larger and have a flatter back. They do look very much alike though!