XTR or. . .

[hamster]

The kids bike will have XT.
I wouldn't sacrifice function for form but it'd be nice to have both wouldn't it??

Personally I wouldn't bother - they do daft things on their bikes and chuck them over onto the mech etc. I would go for something cheap and made of steel as it handles being mistreated much better.
Being steel you can bend it back after some eyewatering crash. Alu just breaks. Acera or Alivio all the way!

 

[IDB1]

It's only for them to come riding with me.. they have a couple of BSO's for daily use