Child account FC25 on Switch

Hello.

I have successfully created a child EA account. I have purchased FC25 on the Nintendo Switch. I cannot link the child EA account within the game and therfore cannot get online. Both options given for linking accounts do not work.

First option requires date of birth entered which immediately fails as my son is 11.

The second option is a QR code for logging on via a phone. It asks for an email address. If I enter my email address which is the one linked to the child account it doesn't work. If I enter the EA ID for the child account it also doesn't work.

Please help. In the UK if that makes any difference. 

PS. I've got to the point of dreading my children asking for any games that are online in anyway (basically all of them). It's always so complicated and time consuming getting it to work.