I don't know if it's possible to predict in advance, because there are so many variables, not all of which are under your control.
For instance, if the people who are running the fair don't do a good job of promoting it, or promote it to an audience who isn't primarily interested in what you offer, it probably wouldn't be a good deal for you. But if they are able to bring in a lot of people who are
interested in your products, it could turn out to be quite lucrative.
I know some people who actually make a full time living with their crafts, simply by selling at fairs and shows. They live in a rural area where their day-to-day expenses are relatively low, and do a show or two a month, traveling in an older RV they picked up cheap. Gives them a place to stay at the show, plus plenty of storage space to transport their products (and space where they can make/assemble more products "after hours" if needed during multi-day shows). So in other words, just because you don't live in a big city, that doesn't mean you'll never be able to participate in trade shows again... if it turns out that's a good way of marketing your products you can find a way to make it happen.
But I digress...
If you decide to go, make sure you have plenty of business cards with your contact information (website URL, email address, phone number, whatever channels you use to sell your products). Put together the most attractive and eye-catching display you can. Be sure to tuck a couple of business cards into the package if someone buys from you, and try to get everyone who stops by your display to take a card. Since you say your primary goal is to build ongoing traffic for your website, you want to make sure that people who stop by your booth go away with the information they need to find you again once the show is over.
You'll also want to promote your own appearance at the show ahead of time. If you have social media accounts (Twitter, Pinterest, Facebook, whatever), mention that you're going to be there. Maybe even offer some sort of special deal to website visitors who stop by your booth and mention a special code, or something like that. At the very least, invite your followers to come to the show and bring their friends. Post pictures of the kinds of things you'll be selling at the show. (Pictures tend to attract attention.)
Honestly, if you can swing it, I think it will be a good experience for you. It will give you more exposure and it will help you hone your in-person selling skills.
And it's not just about the sales you might make there. If you really listen to the comments (particularly the objections) that people raise, that will help you refine your online marketing to address those objections (which will help you sell more product in the long run). And if there's something that really seems to resonate with your booth visitors, you know that's something you might want to push harder online.
To my mind, there's very little that can beat getting "up close and personal" with your target customers.