re: Is 529 best option for building college savings??

You can. Sarcasm font.

However, I do agree with the 529 being somewhat inflexible. I also don't like the idea of a custodian account since when he turns 18, it's his. I'd prefer it to continue to go through me. It's my money, it's simply earmarked for him.

I'm simply planning to diversify. I'll put a little in a 529, save some in a brokerage under my name, and hopefully can pick up a rental unit.