All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Any Muslim child who dies is destined for Paradise. This is supported by a Hadeeth on the authority of ‘Aa’ishah where she mentioned that the Prophet , was called to lead the funeral prayer for a child from the Ansaar (the Madeenan helpers). She commented that this child was one of the birds of Paradise because he had committed no evil and he had not even perceived it. [Ibn Maajah and Muslim]
In his explanation of this Hadeeth, Imaam An-Nawawi mentioned that all reliable scholars have unanimously agreed that deceased Muslim children are destined for Paradise because they die before being competent for religious assignments. However, there are some unreliable scholars who have refrained from mentioning the ruling on deceased Muslim children.
Allaah Knows best.