A brief critique of each of your "maybes":
Bow of Nylea - a reasonable card for the long game. You don't want too many non-creatures, though, because you're trying to set up a critical mass and because Lead the Stampede is too good not to play. I don't play this, but I have considered it.
Eladamri, Lord of Leaves - Main or side, worth the slot. Great with Chord of Calling; sucks with Wirewood Symbiote or Quirion Ranger, though. Also prevents Ezuri from regenning most of your team. Eladamri doesn't have shroud, but his rules text makes it look like it.
Elvish Guidance - Worse than Gaea's Cradle, and usually worse than casting Sylvan Scrying or Crop Rotation for Gaea's Cradle. It might be worth playing, though. Just be aware of your creature count for Lead the Stampede.
Fauna Shaman - I've been unimpressed, due to summoning sickness and general lack of being able to fetch up a real combo. Late game she could be fine, but I'd rather just be drawing more cards, rather than cycling away creatures for slightly-better creatures.
Greenweaver Druid - If it costs 3, it better tap for a lot more mana, I think. Joraga Treespeaker is basically this card but better.
Heart Warden - Not my cuppa, but you could do worse. You'll basically never cycle this unless you've got extra mana in response to a pyroclasm/anger of the gods/toxic deluge.
Quest for Renewal - almost certainly not worth the non-creature slot.
Rings of Brighthearth - I'd rather just overrun once with another creature in play. I want to improve the consistency of getting to the first overrun before I worry about any others.
Steely Resolve - shroud is barely good enough on an elf that you can Chord of Calling for. It's really bad on a non-creature.
Sylvan Scrying - Abso-fucking-lutely.