What is a good size chess board for an eight-year-old? I'd like to buy my nephew a folding wooden chess set for his birthday.

When I played with my own children when they were smaller it was hard for them to go more than a few minutes without fidgeting and jiggling that inevitably upset the board, so I am pretty sure that the larger the pieces are, the better the experience will be for everyone.

Is something like this or this 10" set likely to be too small? Or is it better to have something larger?

I want a folding set that he can safely put away with the pieces in it. I don't really see the point of a magnetic board, I'd rather just have heavier pieces. I'd be glad to hear out any experiences and advice.
Larger pieces and board may help to keep a better overview for a beginner. As soon as his interest in chess becomes more serious, he will start to be careful with the board, so I wouldn't pay too much attention to the weight of the figures, most sets aren't heavy enough to withstand mechanical force (unless you choose marble pieces).

I'd recommend around the 14" or larger, keeping in mind though that as long he's not actively playing the set could just be one more toy cluttering the shelves in his room.