We gave a party a few years ago for our 25th anniversary and my 50th birthday (they were 3 weeks apart). Notwithstanding the rule of etiquette not to mention gifts in any way, not even "no gifts, please," on an invitation, we did it anyway. We know the rule, and I agree with it, but it was not only an attempt not to seem gift-grabby, it is definitely the convention in our community in the last few years. People do often give parties for their own anniversaries and their own (or usually their spouse's) major birthdays, and they ALWAYS put "no gifts, please" on the invitation. It's against the rule, but it's nearly universal here lately, so we did it.
And what happened was exactly what we knew would happen: most people brought nothing, and some brought a little gift (bottle of wine, candy, etc.) like you might for any party. Our very closest friends gave us bigger (mostly group) gifts -- but they would have anyway, for the big milestone, even if there had been no party, because that's how we all do for each other. It's always dangerous to say, "I am sure no one was offended" (no, you're not, really, especially if you are just relying on not hearing about it), but I can say that judging from who gave us gifts and who didn't, no one did anything different than they would have done had it just been a no-occasion party.
If we hadn't put "no gifts, please" on the invitation? I can only guess, but I imagine that maybe more people would have brought some kind of gift, but even then it would have been small things -- picture frame, book, plant, charitable donation, etc. -- that are pretty much hostess-gift size stuff. That is what happened when we had parties for our 40th birthdays, before "no gifts, please" got to be the norm.
So I don't think you have anything to worry about. Just know your audience and remember that people will base their expectations of what to do on what is the norm in YOUR community, not ours.