After much searching, I found these little fire engines and a digger for the little boys.
A fire engine each for the twins (in an attempt to avoid any arguments), and a digger for little C. In actual fact, the fire engines might be needed to put out the fire which will occur if the twins decide they would prefer their coins to come packaged in a digger.
I found a lot of papercraft cars, trucks etc but some of them involved a great deal of effort to assemble and I was looking for something quick and easy.
These took only a couple of minutes to print, fold and fill with chocolate coins.
I hope they like them and if they are demolished in the process of getting to the treats inside then it doesn't matter.
Pleased to report that no fires had to be extinguished and all seemed happy with their respective fire engines and digger.