Hi Friend,
I suggest you talk with her about it, or have you already? Come clean, in a heartfelt way. Let her know how important she, your union and anniversary are to you. Ask her how she would like to celebrate. Tell her your dilemma re the guild meeting and your hopes for a wonderful time together as well as being able to further your love/work/needs/etc (plug in the right words) for knives.
Even if there is already tension over the subject, I've found, that honest sharing from the heart, with sincere interest in hearing from the other and a commitment to soul searching together, usually allows a win win solution to arise. If you have more (or at least as much) stock in its being a mutual discovery process as you have in your preconceived wishes, than it can often be more fulfilling than what you hoped/preconceived going into the discussion(s).
Can you tell I'm a romantic? Indeed, whatever romantic qualities you can muster would be advisable....to aid achieving maximum happiness for both of you.
All the best, Phil