Alicornutopia

Yeah, collective-nouning Stevens is hard.

A quietness?

A whisper?

If you wanted to play up the Voice aspect you could call it a "murmur" or a "chorus" but I feel that is rather unfair to the nice Steven.

Punny question, can Lazarus notice a Koylas' absence?

An argosy of Jasons.

...My first thought is "whisper" because Voice and because child Stevens speak softly.

Two votes for Whisper!

A susurration of Stevens?

Why are they collectively called Stevens anyway? None of the examines who go by their original name have that name.

In any case, some bellspawn ideas, in order of Bell appearance in Effulgence:

Stella: planets
Shell Bell: sand grains
Sarion: Elvish for smallmages would be confusing; drakes could work for Ansharil
Phoenix or Raven: feathers
Stormy: clouds, droplets (unlikely to be useful if Effulgence wiki is accurate in reporting her as asexual)
Katie: seeds
Butterfly: caterpillars

Edit: I missed the in-story starlings for Stella; those work much better. I think sand grains work better than something molluscy for Shell Bell’s kids, though, because those can be the product of shells and also connect them to Pearl

Stormy is not particularly less likely to want children than anybell else, she just won't arrive at them in the conventional way.

Seeds (I'm making it seedlings) and caterpillars are Obviously Correct. I already had caterpillars down in the spreadsheet; Katie was "buds" but seedlings is better.