BASEBALLINCT,
Yes, ignore the email, but don't ignore Headfirst. Don't think too hard about their motivations for sending it to you, the text of it is a marketing gimmick and it sounds like it worked? And that's good. HF is an outstanding showcase organization. So let's move forward with your other questions.
Attending rising Jr. summer? Sure, but keep in mind next summer those coaches at HF will be hyper focused on 2018s, but they will stop to highlight a 2019's name as they go from one field to another, of a kid they want to follow and check up on next summer in 2018. If you're son is projectable, has size, it can also be a benefit to go as a Jr. If you believe however, if he is borderline, may not stand out on the field and will just blend in with the other 200+ players, save your $ and go next year as a rising Sr.
But if you believe he will stand out as a rising Jr. and can swing the $995, make sure son has had many, many "dress rehearsals" at smaller, less expensive showcases, and most importantly game experience. HF is not a "hey, let's go give it a shot and see what this showcase stuff is all about" type venue. I see you're from CT so, you should be able to save a lot in travel, hotels, etc.
As far as the ACT/SAT scores go and not having them yet? Not a deal breaker for me. AS LONG AS YOU BELIEVE THOSE #S WILL BE THERE SOON AFTER so you are not wasting your money and a coach's precious time who might be intrigued with your son and want to follow him thru his Jr. year.