This might be a good and cheap craft for groups of kids- maybe older kids if you aren’t looking for perfect results.
I think thse are quite stunning,
Taking plain terracotts or clay pots and making them into something almost elegant with a simple 9 and cheap!) tube of puffy white paint. What a great idea – for complete instructions visit DIY Puffy Paint Terra Cotta Planters
I think you could also do something nice with kids with bit of colour- use 2-3 colours and make pop-art flowers, bright fish, starts, etc. A cheap and cheerful take it home “loot” bag could be one of these decorate pots with a colorful flowering plant or bulb inside.