My only experience of this is my sister ...she had 2 kids, got divorced, met her current guy (didn't marry), had another kid and registered the Dads surname...
He used to get asked at school...''why has you mum got a different name to you'', which used to upset him..
She wanted to change her name, but didn't want to upset the 2 older kids ...
What she did was change to a double-barrelled name..
Everybody's happy and I think it cost her about �50 at the solicitors...
So you could have the best of both world ...your old name, and your new one ... and your child won't be ''bullied'' over it.