Seaweed hacks! Brook’s suggestion works in the best "if you can’t beat ’em, join ’em" way:
Give your kids big sheets of nori seaweed when they’re at the age to rip up paper and stick it in their mouths. Same ripping and exploration experience, no choking hazard (the seaweed literally melts in their mouths), some phytonutrients get ingested, and they might maintain a taste for sea vegetables. At fifteen, my daughter will still choose to eat a snack of nori!
Amazing. My kids shun eating "leaves" of any kind except seaweed. When wrapped around vegie sushi, they gobble it up. And yet salad is looked upon with scorn. Go figure.
You should be able to find nori in any natural foods or Asian grocery store.
Related: Let them eat seaweed