After they were all cleaned, we took out the bad ones and started to put in some cement for the foundation. The only big enough bucket to mix it all was the crab. So that one has now been sacrificed for a higher purpose.
Lina and Mees were obviously very happy to help out and supervise.
By the way, we think we have found a solution for all the remaining sand: we still have to level out the garden and we will use it to fill up some of the plant borders we will build up at the back of the garden..