Front Cover for Children's Novel Required

I have a completed novel aimed at 9-11 year olds, therefore require appealing, contemporary, realistic illustrations . The main character is a 10 year old boy (caucasian) and a 10 year old girl (asian); they are both at primary school. This will eventually be produced for Kindle.

The text is 57 A4 pages which will translate to probably around 120 pages of text. I am happy to have full page ilustrations as appropriate.
Please suggest how many illustrations you feel may be desirable and bid accordingly. Please use clarification boards if you need further information.
You can bid for just a front cover design should you wish. This may be a multiple freelancer project.

Many thanks