I noticed that you're in Florida. We lived in Titusville when my boys were in the early grades. Both of my sons were in the gifted program there. (They are now in their late 30's, so that was a long time ago.) At the time, Florida was way ahead of most other states in providing a good program for these types of students. They were able to do it because they recognized that gifted students have special needs that are frequently not met in regular classrooms, and so they funded the program in the same way that they would other special needs programs. My kids did well there, and when we moved there were gifted programs, but not as great as the one in FL.
Boredom is a real concern for gifted kids. Sometimes they just kind of turn off and fail to excel to the extent of their abilities. It's a real waste and a loss for our communities when some of the brightest minds are wasted because of mismanagement in their early school experience. Sadly, a significant number of high school dropouts have been identified as gifted. As a parent, you might find it worthwhile to go to the library and read whatever you can get your hands on about gifted kids.
As for posting it on Facebook, I wouldn't. There is nothing to be gained by it, and one of the worst things you can do is make a kid feel socially "different", including in a good way. From the earliest grades they will encounter other kids who resent them for the simple fact that teachers tend to like them and give them more attention and more rewards, and also because sometimes other parents make comparisons or teachers grade on the curve, and the high achiever is going to throw off that curve for the other kids. When my daughter was in kindergarten the class was rather large and the teacher actually recruited her and one other girl to help teach some of the slower ones to read. She had mixed feelings about that, but luckily they didn't seem to hold it against her. There is a strong social instinct to want to belong, and sometimes kids will deliberately fail at things just to avoid the negative response that they might get from some of the other kids.
The main thing about posting this sort of thing on FB is that it's just one area of a kid's development. You don't want to give him the impression that it's enough just to be brilliant. He also needs to be caring, friendly, hard working, etc. and needs to know to appreciate those qualities in others, even if they might not measure up to him in brain power. When we were given our son's high test scores as you have been, we were told not to even tell him the numbers because it's too easy for a kid to sort of think that the numbers themselves are a measure of himself as a person. It's just one aspect of who he is. I agree with quiltmom04 that you don't have to toot his horn - others will definitely notice his achievements all along the way, and they will be much more impressed with team spirit and hard work than with test scores. Rather than focus on the scores, focus on what he is learning day by day; help him to explore the many opportunities that are available. At the same time, let him still be a regular kid. Soccer, swim team, band, volunteer work and all sorts of other non-academic things can also enrich his life and help him to grow into a well-rounded individual, and - just by the way - look good on college applications, too. It's not too soon to notice that an officially high IQ never got anyone into college, all by itself. Wishing your little guy the best possible future!