That's not a bad score, and it will not affect your chances of getting into the summer seminar one bit.
If you are able, take the SAT and ACT again when you are a senior. Your new scores will update on your record. If you didn't prepare for these tests the first time, make sure you
take practice tests and prepare for them the second time. Endeavor to get a better score the second time around.
The Naval Academy Summer Seminar (NASS) program
is more of a marketing and outreach thing. It has no bearing on whether or not you ultimately receive an appointment.
It is geared toward H.S. seniors who don't know much about SA life and is designed to steer them in the direction of USNA. It is for all intents and purposes, a protracted college visit.
This is not to say that you shouldn't go, or shouldn't want to go. Go ahead and apply for NASS. This begins the admission process and will get you assigned an official candidate number.
What should be stressed here is that if you do NOT get accepted to NASS, it is no big deal. It will not affect your "chances" one bit. Every year, a LOT of very well-qualified candidates
get passed over for NASS, because the USNA already knows they're serious about appointment to USNA.
The Naval Academy Candidate Visit Weekend (CVW) program
If your application is really strong (and you have it half complete by the end of the summer), some time in the Fall you may receive an invite to one of the scheduled Candidate Visit Weekends (CVW).
This is one of those first "litmus tests" to let you know that the USNA has taken an interest in your application. If you cannot attend, it will NOT be held against you. If at all possible however, you should attend.
I am not saying that you should attend because it will "help your chances", but rather because it will expose you to academy life on a snapshot scale, as you follow a Plebe around for a couple of days.
If you're "all-in" already, the CVW will probably make you wish you were already done with your senior year and at the Academy. If you're vacillating either way, the CVW may actually be one of those things
that makes you decide "holy crap, Academy life is not for me!". It's a Thursday - Saturday thing, and it will cause you to miss a couple of days of High School, to be there.
The Candidate Fitness Assessment
If you do end up at NASS, be advised that they will conduct the Candidate Fitness Assessment (CFA) while you're there. Quite a few candidates come away from NASS with less-than-stellar CFA scores, only because they
haven't been training to do their best on this set of physical tests. Many of them end up re-taking the CFA later in the year, to improve those scores. It is something to think about. If you're planning on going to NASS,
then you should be doing practice CFAs before you go, and should have a good idea already as to how you will perform. Your CFA score should not come as a surprise, in other words.
No one knows for sure what the percentage of importance is for each part of the Whole Candidate Score equation, but think about your CFA as one thing that you can keep improving upon.
Conversely, those first 6 semesters of High School are already over at the point of going to NASS, so there's nothing you can improve on with that academic score!