I would not use an 8va clef in violin music. Instead, would use an "8va" marking where necessary.
In 35 years of playing violin, I've never encountered anything but treble clef, outside of some moveable clefs in baroque music. I've encountered the suboctave treble clef (8 on the bottom) in classical guitar music and the tenor part of vocal music, especially English madrigals. I've never encountered the "sopranino" (8 on top) clef before; Wikipedia tells me I might have if I played recorder or penny whistle.
Violin practice is normally to prefer ledger lines especially when there will be 4 or fewer ledger lines, and when the section using ledger lines will be brief, like maybe just a few notes. Longer passages that would have 4 or more ledger lines can be written transposed with "8va" marking. Just try to avoid shifting back and forth between 8va and non-transposed too often in a short time.
In this piece, there's no need for 8va for the second violins. Note, the goal is not to "tidy up the score" and remove unsightly ledger lines; the goal is to do whatever lets the players play it most easily. Violinists are quite used to counting ledger lines, at least up to 4 or maybe 5. As for the "15 clef," I couldn't even imagine what to do with it. I had to search Wikipedia to find that it's in fact two octaves above written, not a fifteenth. This would be a welcome time not to notate it at pitch, but it's quite enough to write the D with two ledger lines and add 8va.
To answer the core question, for instruments that should switch clefs (viola and cello when appropriate), I don't think any text instructions are needed. But if the clef change comes at a line break, I would add a "courtesy clef" at the very end of the preceding line.