Here's another perspective. Think hard about why he wants to red shirt him. Our son is 4 and likely HG+. We are skipping preschool altogether. He can read. He is happy doing 2nd grade math. Our son has excellent social skills with peers (older kids and adults he respects). He can tolerate adults he doesn't respect in limited doses for a limited time period (I.e. 2 hours, not 6). His coping skills get better every month as he matures.
That being said, he is extremely active and doesn't tolerate forced boredom well. I think sending our son to school at this age would leave him with a negative impression of school we'd never shake.
We are taking it year by year, but with his learning curve, we are thinking we'll probably homeschool. There is an excellent and welcoming homeschooling community here that has provided a wonderful multi-age set of peers for socialization. I have no doubt he's thriving at home in a way that he wouldn't be able to in school at this stage. Your mileage may vary, but keep in mind grade is just a number until you put him in the school system.
