How safe to live in Nigeria with family

Well come Mr. Jai to Lagos,

How safe for living,
Lagos is safe, there are people are staying as much more than 20 years period,
based on the persons activity depends

How about kids education
There is an India Language school is there for Kids Education, your kids can Join there and continue.

How is living cost
Living cost compare with India, most of the goods selling here is imported the cost will be comparatively 2 to 3 times higher.
by an regular lifestyle with wife and kid need the local expenses will be around 200 to 250K NGN or ( like $500 to 700$)

If you need furhter any details Please let me know

And what about malaria?

You might want to do your research.   Nigeria is considered a high risk destination by most countries travel advisories.

I used to travel quite often to Nigeria and the security precautions were quite stringent. 

But then again it varies depending on your lifestyle and what precautions you adopt.  Just be mindful that corruption is rampant, infrastructure is bad and the police forces woefully inadequate.