When I was younger, I worked in the music business doing concert tours for almost a decade (merchandise, production and then tour accounting). This is not how things work. Agents sell shows to experienced promoters, not first time show buyers. Agents do NOT assist in booking travel or obtaining visas. They provide the promoter (buyer) with a large contract and rider which lays out all of the artist requirements and the promoters own production manager takes care of the details.
The cost for a one-off show (not a routed tour where the band is already on the road) is usually double the cost. Santana's guarantee is over $300,000 for a tour performance and more than double that for a one-off show. As I have already pointed out previously, he is doing a residency in Las Vegas and the dates conflict with Boomerfest. The most recent charity concert was produced by long time promoters who were brought into the fold by heavyweights like Harvey Weinstein and Steve Burke.
There is no agent in the world who will sell a major act to a promoter who is doing a first-time fesitval in a foreign country, in a small town of 36,000 people. The mere fact the announcement of the line-up keeps changing is proof enough that this is not going to happen. In the end, Boomerfest, if anything, will be nothing more than a Beach Boys concert or similar type act on the beach playing to less than stellar numbers.