I've installed electrum and there is an address in my wallet's "Receive" tab. I could just post this address as a bitcoin: link, and that would be all that's required to receive donations, correct?
Yes.
I have read that it's highly recommended *not* to reuse bitcoin addresses, to preserve privacy. I honestly do not expect to get very many bitcoin donations at all - could I simply change the donation address manually if I receive a donation to the current address?
Yes.
Is there any reason to be concerned if I receive a few donations to the same address before changing it?
No. You will lose some privacy, but you are already losing privacy by having a public address.