Yeah, I wouldn't get guilders. They can't be used anywhere else, that I know of. As you said, if I get euros, I can at least use them in Europe!! (I'm planning a trip to Germany in 2020, so I need the euros anyway).

I'll do what Sammy suggested: Get mostly dollars, and keep a few euros, if needed. I think I have about €30 buried in my sock drawer that I'll bring.

Thanks to all for the advice.