tbh the price difference between the standard and XL is not much, if he would enjoy using a XL more than a standard 3DS and doesnt really mind paying a extra £20-£30 i would suggest an XL, same for the 2DS it isn't really cheap enough to warrant consideration imho this is based on second hand price, if your not in a rush i would suggest hanging on a little bit and waiting till you get that killer deal price on either model like i picked up a spare 4.x 3DS standard for £30 with Mario 3D Land and another 4.5 standard 3DS for £40, i wouldn't of picked them up if they were not bargain prices though
plus i would still recommend you keep an eye out for a 4.x console, you could take a nand dump then update and if you ever need to downgrade you have the option too.......say if your current 4.x console is damaged or lost and the price of 4.x consoles keeps going up