A recent magic show birthday party I did featured a mix of commercially purchased and home made Emoji party decorations.
One of the party activities for the kids was to make Emoji balls.

Mom & Dad helped the kids fill yellow balloons with rice using a funnel in the balloon’s neck. The kids then decorated the rice filled balloons to make their own Emojis. (Filling will go faster with a wider bore funnel.)

Parents might want to experiment with different markers before the party as the Sharpies used here smudged a bit. Expo low odour dry erase markers might be a good choice. The dry erase ink actually becomes permanent on latex balloons for reasons you’ll need an organic chemist to explain.

Parties with structured activities like this are always better for kids than the ‘free range’ variety. Bravo Mom & Dad! Google ‘diy emoji stress balls’ for more info.