Don't give it away!
In my opinion your best bet would be to announce your immediate retirement with minimal turnover time and the rest of it taken as vacation. Leave the office after 48 hours and don't return. In fact, see if you can take an extended sabbatical and retire from there without even coming back. No one will raise an eyebrow when you clean out your desk for those things that you'll use during your "sabbatical".
This strategy gives you an opportunity and avoids two problems. Your "shock & awe" approach may inspire management to make you a better offer to "ease your way" into retirement. Part-time, telecommuting, consulting, all might be suggested as a concrete way of proving that you've been a top performer. You might even get paid to train the whole staff on how to apply your years of accumulated wisdom.
The first problem is that you give away your hand (and your eligibility) by announcing your retirement any more in advance than the minimum required. If management was planning to offer one of those unpredictable buyouts, you'll have missed the chance. The second is that, as mentioned, you risk being marginalized and ignored. You can get more than enough of that at home on your own time!
The second problem is the office farewell. This approach will truly separate your friends from your co-workers. If they want to spend time with you, they'll invite you to a retirement lunch. If it happens a month or two after you retire, then they get to regale a fresh audience with the latest office gossip. No one will be angling for your office or kissing up in the chance that you have something else to give away. You'll be relaxed & mellow, in the perfect stress-free frame of mind to enjoy this appreciation. And you get to sit there serenely and smile with the thought that, unlike them, you have the rest of the day off!
I made the "mistake" of taking a month's "trial retirement" vacation before I decided to retire. I had so much fun that going back to work was a major annoyance.
As for the ceremonial departure, I've watched hundreds of military retirements over the years. Many of them were monuments to ego that occupied the efforts (and fundraising) of the office for weeks. No productive work got done while the caterers were consulted, the ceremony was scripted, the rehearsals were held, the farewell dinners (!) were organized, and the gifts were bought. On "the day" the usual reactions were "Are you still here?!?" and "Retire already!".
Others were triste, almost sad. No one objects to seeing women break a teardrop or two at a time like this-- but when you watch four multi-decade battle-scarred testosterone-drenched alpha-male American heroes blubbering on the stage in one month, it gets a little depressing. Most regarded it as "closure" while I saw it as trauma. I think closure comes when you have plenty of well-rested leisure to reflect upon your accomplishments (and failures) and to set your course for the next stage of your life. You'll never do that while you're in the process of retiring.
So get out at the last minute with no warning and as little fanfare as possible. Soak management for as much money & guilt as you can but don't let them "honor" you with any ceremonies. Clean out your office at 2 AM if you have to.
Here's another surprise. In my two years of retirement I've built friendships with a number of coworkers. It started as a request for a recommendation letter, followed by a question or two, and ended up on my back lanai with a frosty beverage while we worked through the issues. For whatever reason these people hesitated to develop a friendship while we were working in the same office. Politics? Once we were no longer possible threats to each other, friendship blossomed. After all the frustration of work, this has been quite gratifying.
