What does an unassuming American grandfather look like? I'm American and old enough to be a grandfather, but appearance-wise don't fit the image of what most people think of when they think 'American'. I'd say just be unassuming, period, and don't act nervous or shifty.
When I used to air travel a lot back in the '80s and '90s, I carried a Victorinox Spartan right onto the plane in my pocket everywhere I went, which included South Korea, Japan, Taiwan, and Hong Kong, as well as various US airports, without problem. Obviously, that's now impossible. Last time I flew, back in 2003, I had only a carry-on bag, so I took no knife at all with me, and went knifeless for a few days.
If I air traveled again nowadays, I probably wouldn't take any more knife than a Victorinox Classic in my checked-in luggage (if I had a checked-in bag). Otherwise, I'd simply forego carrying a knife again during the trip. Sounds blasphemous, I know, but at least I'd have nothing like that to potentially stress over.
Jim