hidden server/polite blacklist?

is there a way to control a specific users access to a server without telling them they are blacklisted? like to return the default message they would get if the server was not running? i want to control my nephews access to my server without him knowing or getting the 'you are blacklisted from this server' type message. i love to play with him (some of my buddies do too, he is a super cool kid), but sometimes the server is just up for 5 mins to test/update a plugin or config, or its full of my buddies who are likely saying things my young nephew shouldnt hear lol. at those moments its not cool for him to be able to just pop up and i wish i could just lock him out somehow without any visible indication on his end, and unlock him when its a better time for him to come play.

thanks for any info/help

 

tell hes mom when he can play.

 

lol funny but not very helpful