Making figures out of dough to teach the handicapped, then getting rid of them

I work in a centre for the mentally handicapped. Some of them find it difficult to move their fingers, so we decided to teach them to make shapes (of non-animate things) with modeling clay, but it is too difficult for them. So we replaced that with something like flour that is mixed with water, so it is like clay in their hands. After they have played with it we dispose of it. Is that permissible?.

Praise be to Allaah.
There is nothing wrong with what you have mentioned about making shapes of inanimate things, even if they are made out of flour or dough, in order to teach the mentally handicapped how to move their fingers. But it is better to make some use of the flour after that, even if it is by drying it and giving it to animals to eat, so as to preserve the blessing and not waste it. But if you cannot make any use of it, then there is no sin in throwing it away and getting rid of it. 
Some scholars have stated that it is permissible to use some kinds of food in shampoo and similar things that are used for washing the face, and it is known that these things are washed away with the water and no further use is made of them. 
The scholars of the Standing Committee were asked: 
In the marketplace I see a kind of shampoo that the grocery store owners say is made with eggs, and another kind that contains lemons. Is it permissible to wash with them? They replied:  
It is permissible for you to wash with shampoo and water, even if it is mixed with lemon or eggs, and to wash with soap and the like with water, to help remove dirt.  
Fataawa al-Lajnah al-Daa’imah, 24/108 
And Allaah knows best.