The only thing to consider is that you will be kidding 4 goatlings all at the same time - your herd will explode in numbers in 2 years... better to start with a mix of ages and take it slower. Just my take on it.
Also bringing up kids without nannies (not necessarily their mums) will make it much more difficult to bring them up as "goats" and not as "pets", they will learn respect and how to take their place in a herd much easier with older girls/milkers around.
Had my kids out yesterday in the field with some goatlings and the old matron (who fights with all the other younger milkers because she still thinks she is boss, but she isn't anymore) and she was so happy to sort out the youngstock! While I was there the kids just jumped around me and up onto me, and the goatlings joined in too. As I left they just all settled down to "organised" grazing. You can't beat a (goat)granny in doing some babysitting for you!
Ideal start IMO would be nanny with her female kid plus a goatling, again not necessarily nanny's daughter.