'Open Day' Competiton

Hello Everyone
We hope to add a new competition for our Open Day on the Allotments this year and I need some advice.
The proposal, a bit of fun, is to see who can grow the most spuds in a bucket!!
Potatoes will be provided, one each entry, and planted in a standard builders bucket (usually 3 gallon size). Total will be weighed on the day.
Possibly with a separate section for children.
Anyone got any experience of this we would love to hear from you for guidance and ideas.
We thought maybe a second early spud as we hold it in August.
Thanks  Andy