Hello, first time poster, stumbled across this site by accident and its great!

Can someone please advise me? I plan to take my son to Nigeria in the summer. I have got him a Nigerian passport and hes got a british passport. Will I get into trouble at the airport if I use both passports? Like use the British passport to leave at heathrow, use his Nigerian passport to get through immigration at Lagos, then not sure what to do when we are returning...do I now present both passports at Lagos when am returning to UK, cos if I present the Nigerian passport, there's no UK visa and his British passport has no Nigerian visa ...any suggestions...dont want to get into trouble with the authourities..UK or Nigeria.
thank you