Hard to say -- "formal" usually equates with the classic citrus/herb style of something like 89 or 127.
After that, "formal" is a purely subjective term... whatever makes you feel comfortable and elegant. That does sound like a special event! If you can get to a Floris store, you may find a bottle of their discontinued Vetiver, a warm, woody scent. I truly appreciate Elite, which is a great lean-green scent. I didn't care for JF due to its ozonic note, but you might find things to appreciate in its green and woody notes. Santal -- too vanilla for me. Once you rule out the citrus notes, you've eliminated several of the Floris products (Cefiro, for example). You might try Rose Geranium, a classic British geranium-rose sort of scent with a bit of wood.