If you're anything like me, you cringed when you saw this was part of the Children's Week meta. Take heart! It's not all that bad. I have a few tips to make it easier.
1) Remember to have your orphan out.
2) The orphan is critical to success, remember to have it out.
3) Put the orphan whistle on your bars in order to facilitate remembering to have your orphan out.
Follow these tips and I'm sure you can avoid the mistakes I made.
The achievement took around three hours, including some interruptions. If not for my forgetfulness and distraction, I think I could have gotten it done in two or less.
By increasing difficulty, I'd rank them as EotS-AB-WSG-AV. None of these are truly hard, but are instead various mixes of opportunity and competition. AV has few chances per BG, a lot of competition, and BGs take a while. In contrast EotS is faster, had many chances to carry and capture the flag, and has fewer people.
If you're willing to play 'wrong' in order to increase your chances at the achievement parts, consider these tactics:
AV: Don't defend your attacks, but instead allow recaps for more chances to attack.
AB: The second person to a defended node has the advantage. Ninjaing a poorly defended node is more rewarding than ever. I learned this after I parachuted into the mine to find nothing but a squishy hunter.
EotS: Defend the center to allow everyone a chance at the flag.
WSG: Let the other team get to your flag, and then do horrible things to them.
P.S. Don't forget your orphan.