At what age do you think it's safe for a kid to have a taste of inihaw (like isaw, barbeque, etc)?

I would say not until they are 7 years old and up. Grilled food are more likely 'unsafe' especially if not properly prepared and actually can cook food unevenly especially those that come in big chunks like our all-time fave chicken bbq or liempo. Children under 7 y/o are at increased risk for food poisoning and related health complications. This is because their immune system is still developing and they cannot fight off infection as well as adults can. Young children also produce less of the stomach acid that kills harmful bacteria. This makes it easier for them to get food poisoning. So better delay the introduction of these type of foods. Anyway I'm sure their interest is not that great yet for these "adult" foods.

If these are prepared at home, maybe around 3 or 4 years old is acceptable. Just make sure you don't burn it so it will not be as carcinogenic as overly burnt foods. I think if you are sure that it's properly prepared then let the kids enjoy it.