For what it’s worth, this seems like the fatal flaw in the OP to me. If you need input on whether something is good to do, it’s very easy for someone to reply “yes” or “sounds good,” so just ask for input. If you don’t need input, just send an FYI instead of the weird asymmetric asking-for-objections-but-not-approval.
We’re informing the manager of our intention, but we already decided it was a good idea at the engineering level. We’re not really soliciting input, eg, whether that’s a good idea or not. However, there might be conflicts we’re not aware of, eg, “Wednesday is bad, since there’s a demo that day.”
Asking if there are concerns is soliciting that information — but being clear about what you’re asking.