Congrats on getting married NewbieBulbs! Late blooming tulips should be in bloom towards the end of May, in my experience Viridifloras tend to be around the longest (plus their colours are more intense towards the end of their stay).

Alliums are another that are around through May-June, there are some fantastic varieties, the giant purple rounds (purple sensation, gigantium, globemaster) and their white counterparts would certainly stand out. Also allium bulgaricum would (to me) be perfect at a wedding, as they look like little bells, I've mixed those in with christophii in the garden.

Hope this helps. :)