He died and left behind a wife, two sons and three daughters

Firstly: 

No differentiation is made between minors and adults with regard to inheritance. Small children have their share of the inheritance just like adults. 

But a small child should not be given his share in his hand, rather it should be given to his guardian who spends on him, and reference should be made to the court that deals with that, so as to protect the orphan’s wealth. 

Secondly: 

If the heirs are those whom you mentioned, then the wife gets one-eighth, because Allaah says (interpretation of the meaning): 

“In that which you leave, their (your wives) share is a fourth if you leave no child; but if you leave a child, they get an eighth of that which you leave”

[al-Nisa’ 4:12]

The mother gets one-sixth, because Allaah says (interpretation of the meaning): 

“For parents, a sixth share of inheritance to each if the deceased left children”
[al-Nisa’ 4:11]

With regard to the remaining children, each male gets the share of two females, because Allaah says (interpretation of the meaning): 

“Allaah commands you as regards your children’s (inheritance): to the male, a portion equal to that of two females”

[al-Nisa’ 4:11]

Thirdly:  

With regard to dividing the inheritance asked about here, it should be divided into 24 equal parts, of which the wife gets three parts, the mother gets four, and the remainder (seventeen parts) should be divided among the children, with each male getting the share of two females. 

And Allaah knows best.