How to come up with a game idea?

How to come up with a game idea?

Hi Everyone,

I'm very new on this site. I've been searching for information on the internet for ideas on how I can turn my free educational website for children to be more fun. 

I have been a programmer since 1996, so for a long time, but I've never been involved into games. I mainly work on databases, business systems, automation etc. All the boring stuff for kids. 

I created a free website for children as a bi-product of helping my own children with math activities. I never thought that the website would become successful. Over the last year the website has started to grow on it's own and attract more and more children. Although the children like the site, it seems that a little game element with some sort of graphics could do wonders for the children. I'm just not sure where to start. 

So my question really is that how do you take an educational subject and turn it into a game, which is interesting for age 4-11 year olds.

I'm not sure if I'm allowed to mention my website, therefore I'm not including the URL in my post, just in case someone feels that I'm trying to promote my website.

I would really appreciate if you could please help with some creative ideas on how math and educational subjects can be made more fun.

Thanks in advance for giving me your time to read my request. 

Waqas