I don't know your FMQ ability, but SITD would work just fine for this quilt. Except not in the ditches.
The lines I've drawn on the photo show the paths you could take.
It shouldn't take long at all, and it would make it really secure - which given the unknown washing (machine) situation would be a good thing.
I'm sure you can find some nice variegated thread - Joann's has had a display recently of some nice threads. There's a pastel one - and even though it's supposed to be "baby" colors, it would blend in very well across your quilt. And it would give a little sparkle as it would be visible.