One big consideration is that whatever it is I am going to have to carry with me on a airplane and I have known TSA to have problems with craft materials.
Get this:
Jar of 30 colored Kazoos.
Guaranteed fun for kids. Guaranteed insanity for adults. 
Aren’t kazoos used in klezmer music? If so, the adults might appreciate them.
Vuvuzela?
I like the suggestion of a furby, bonus points because lots of people (including me) think they’re not ONLY annoying as shit, but creepy little fuzzballs as well.
Furby for the win. Kids inexplicably love them and they’re horrible in every way.
Maybe a Magic Jinn?:
Get them both Siri and a Furby:
https://www.youtube.com/watch?v=kMIzPDPMAvwAre the Wiggles still a thing? Might as well return fire with an equivalent gift (even though they’re Australian).
Unfortunately, the kids already have Barney. Furbies are definitely looking like a good option. I need to find out if their power source is something available in Israel or if I need to bring bags of batteries.
Gifts that involve cultural diversity that can be described as a “learning experience” are considered of higher value in this game. There’s no actual winning involved, it’s just something my circle of library geeks has all been doing for the past 20+ years whenever we visit each other. The kids (and some cases grandkids, etc.) love it and the adults view it as a geek challenge. Fab merchandise for entertainers the parents absolutely can’t stand, but the kids are enthralled with are considered exceptionally horrific and a serious score.
I love it.