[X] Try to peek into the gates without being seen, and use Bewilder to try to start enough chaos inside that you'd be able to slip through easily with Doppelganger and Take No Heed.
[X] Try to peek into the gates without being seen, then use Doppelganger to take on the appearance of someone on the other side, and use that and Take No Heed to slip through.
[X] Disregard stealth entirely and gallop through the gates, streaking through whatever is on the other side on Shadowsteed before any of the greenskins can react.