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As in, kiddy sized flats. What's out there?
Doesn't need to be a real shin ripper, just decent grip on a good quality body and bearing set up.
I got some Wellgo CNC M142 for my 5 year old, his feet definitely slip less than with his old plastic ones. There was a good run down of options here
Yeah lots of small platform options from Welgo.
I bought my 6 year old some Welgo KC001's (after finding the gravity kids link above also).
They are actually much lighter than the standard plastic ones that came with his bike.
Also, they have studs which give plenty of grip without the shin killers that you get from pedals with pins
I ordered mine from China on eBay, took about 5 weeks to come from memory.
these:

they'll take a few weeks to turn up but worth it over all the previous suggestions (even the chromags) .
Butterfly pedals are horrible and make absolutely no sense and the other ones above are almost even worse. If a pedal body is to be rectangular, the longest edge should be along your foot, not across it.
Wellgo punt out some horrific designs. (as well as the odd decent one)
Welgo KC008

KC008s above are great but tiny. So awesome for very small feet