I worked around this activation by hiding the ChemDraw application itself in the Finder, using the command
chflags hidden "/Applications/ChemDraw 18.app"
and "replacing" it with an AppleScript application, named "ChemDraw Prime 18". The only thing this does is "hold down" the Option key while launching the real ChewDraw app, which instructs ChemDraw to use the older style of activation used prior to v16, where an license code was stored in /Library/Preferences/com.cambridgesoft.plist. You would need to contact your account manager to obtain the license keys to make this work, and distribute the plist to your clients.
Here's the contents of the AppleScript:
tell application "System Events" key down option tell application "ChemDraw 18.0" activate tell application "System Events" key up option end tell end tell end tell
This definitely has its flaws, especially when running under Mojave - macOS will prompt the user if "ChemDraw Prime 18" should be allowed to control "ChemDraw 18", which will probably thoroughly confuse the user - but it's the best that I could come up with at the time.
I'm linking to the admin guide that I found on their site (with difficulty). They provide some instructions for Mac, but it's pretty clumsily written, so I'll summarise:
On first launch, the activation code will be applied, a dialog will appear to confirm, and (in theory) Activate.ini will be deleted. There's no true "silent" activation.