Should my son switch travel teams for a team that attends more nationally recognized tournaments?
That's a great question... However, to give you a better answer, I would need more information. What part of the country do you in? In general there is no need to play the big national events until 16U unless a kid is displaying talents & measureables earlier that would make him recruitable.
Should my son switch travel teams so he can play-up against his grad year peers?
In general, I would say yes. However: A great travel team, especially one run by someone with legit college connections and/or a tremendous ability to develop players is hard to find, and I might be hesitant to leave a team like that. Once in high school, players tend to play with & against their grad year peers. I've seen a lot of kids fall behind by playing 13U when they really should be playing 14U for instance. Again, it depends on some circumstances.
How much investment should we make in private lessons to supplement his team practices and his reps with dad?
Maybe none. Maybe a lot. If you can get some opinions on your son's hitting and/or pitching mechanics from a qualified expert or three, they can tell you if he needs lessons.
When (at what age) should my son attend his first PG Showcase?
At the age where he starts to show recruitable measureables. Pitching velocity over 85 mph, Exit Velocity off the tee over 90 mph, throwing across the infield over 80 mph (maybe over 85) and a 60 time of 7.3 or less... Any of those and preferably a combination of some of those would warrant a PG Showcase. For most kids that is during their Junior or Senior years of high school. Prior to that it is a complete & total waste of money.
Does my son need to establish a profile at each of the big three player ranking organizations (PG, PBR, BF) ... as a parent, do I need to budget my vacation time and discretionary income on multiple showcases and camps every summer for the next 4 or 5 years?
No, see above.
When should my son start attending college summer camps vs. playing summer travel team tournaments?
When he hits the measureable thresholds outlined above.
Will my son fall too far behind in his baseball skills as he is busy playing multiple sports vs. his single sport peers that have already begun to specialize in baseball?
Yes, by 9th or 10th grade, most likely. There are exceptions but usually multi sport athletes fall behind. In 8th grade I wouldn't worry about it yet.