Yeah, I'm with go44. Hitting4dudes - love your pride, enthusiasm and involvement with your son. Glad you posted. Glad to hear your son is a hard worker and making nice progression. But, be careful with the "dad in the dugout" aspect.
I am a HS coach and I purposely take a little bit of a stand-offish approach with parents and have clear rules that they are to be nowhere near the dugout. This starts immediately with our JV level. It's HS. It's time for these young men to learn to handle their own business with as many aspects of their young lives as is reasonable. Once they see the structure and purpose, and their sons have taken the proper lead roles, I become much more open to outside-the-lines dialog with the parents. I have also coached travel and showcase ball. There are different elements in play with regards to parent interaction. In some ways, apples and oranges.
There are so many pitfalls to having the "dad in the dugout" scenario... Actually, I'm a little bit surprised you don't seem to be more sensitive to this considering you have older kids who have all played HS sports. That's not to say that there can't be scenarios where a dad coach makes sense. There often are very good ones. But they must make it clear they are there, at all times, as Coach and not as Dad or son's advocate.
I also coach in the Calif. Southern Section. Agree with backstop - your concerns with missing four months during HS season are unwarranted. The vast majority of best players in the region play both HS and travel. Travel programs adjust accordingly.
We look forward to hearing more about your son's journey. Enjoy it!