FWIW, the QF website suggests that only children under 2 are not counted at oneworld lounges. I realise this is not the AA website, but it is probably the most authoritative quote I can find on this policy:
http://www.qantas.com.au/travel/airl...cess/global/en
Originally Posted by QF
1 not counted as guest
Over 2 years will be counted as the member's guest
This obviously suggests that 1 child under 2 won't be counted as a guest at oneworld lounges. Over 2 year old children are counted.
There is a similar quote for AA, but it is a little more relaxed:
Originally Posted by QF
1 (within North America) not counted as guest (under 18)
2 (outside of North America) (under 18)