I guess "Our grandpa is a kind man." is also a valid translation
Wouldn't kind have a different translation? I mean, I'm relatively new to Czech, but I assume it is as capable of that sort of nuance as English is. The dictionary tells me that "kind" is laskavý.
You are probably right.
My first languages are russian and ukrainian, so there are loads of words that are "false friends" in czech for me
It is close, but 'Náš dědeček je hodný muž' is better translation of your sentence.