Just curious: What is your experience creating and maintaining web sites? I did my first site in about 1994 and my first 'net email address was on ARPANet in the 1980s. IOW, BTDT.
Both maintaining an activity calendar and managing a document repository puts the OP at the beck and call of the anyone wanting updates and changes and expecting more or less instant response. This is in addition to managing users and the inevitable scope creep that the OP will be expected to implement. "Now that we have a web site, we can <someone's idea for new OP work>."
It was about 10 years ago, so memory is fuzzy on details, but I don't have any bad memories of it. Set up a web site for our club using the free point/click tools. Post a few updates a month, post the meeting minutes. It just wasn't a big deal.
Managing users? IIRC, the site was set up to not be public (it would not show up in a search), I just sent out the link to members. Sure, if someone was no longer a member, I couldn't keep them out of the site (w/o changing the link for everyone), and if someone gave the link to someone else, they could see it. But we didn't really care, no big secrets there.
So if the HOA site for the OP is similar, I still think it should be easy.
I also set up a free or low cost forum, that was easy as well.
Of course, it all depends on what the users want. If they start
demanding things (they can ask nicely for anything, they won't know if it's easy or hard) beyond the scope of what OP is comfortable with, just say "no". Problem solved.
Calendar? It's just entries on a google calendar. It's not hard.
And to be clear, while I am a bit of a 'techie' and enjoy digging into some things for the fun of it, that's not what I'm talking about here. I'm talking about easy for anyone with basic computer skills.
DW ran the website at her K-5 school for years. That had quite a bit of interaction and updates, and she is no computer wiz, she's just a basic browse/spreadsheet/word processor user. But she didn't find it difficult or taxing.
I say OP take a shot at using the tools before he commits to the HOA. If it looks like too much, just say "no".
-ERD50