I suggest if possible you have some kind of kiosk set up where they can try out the features of your service hands-on. Scrapbookers and other crafters are "doers" and I think they'd appreciate that. Let them experience it for themselves.
Scrapbookers also tend to be visual people, so you're going to want to have a bunch of stuff for them to look at. Big posters, maybe? Images of happy people doing digital scrapbooking, images of pages from digital scrapbooks, screenshots of the program in action (and so forth). The idea of the images is to attract their attention and draw them in.
If you can do a video comparing digital scrapbooking to paper scrapbooking (maybe even going head-to-head to show how digital is easier or faster or more secure or whatever your primary benefit is), show that on a continuous loop. It's another visual thing that will attract attention. When somebody stops to look, that provides an opening for you to approach them.
Some booths at trade shows also offer cookies, gourmet chocolates or something like that to get people to cross the "threshold" and step into the booth area. Once you get them across that psychological "barrier" it's easier to strike up a conversation. You want to make sure the "bribe" is very enticing and visible from the aisle, but not something they can just reach out and take while walking by. They have to step into the booth to get it.
And, of course, you want plenty of flyers or brochures (perhaps offering a "show special" discount or bonus?) for them to take home to remind them of you even after the show is over.
As for yourselves, I'm sure you already have thought about this, but just in case (because you say it's your first expo): bring lots of water. All that talking is thirsty work. Some high-protein snacks to help keep your energy at a consistent level. And make sure there's more than two of you available at all times (so you can take bathroom/meal breaks without leaving the booth unattended). Depending on what's available at/near the expo, you may also want to pack lunches so you don't have to eat "conference hall food" of questionable nutritional value or go far afield in search of a meal.