Happy birthday to Rosalind and to your daughter too, PLS. Christina, my youngest daughter, is 15 too, and I have lived through many, many parties like the one you described. Have you caught up on your sleep yet?
My oldest daughter, Rachel, was also premature. She was actually due on Oct 30 (my birthday) or Oct 31 (Halloween, which she would've loved) but she came almost two months early on Sept 3 (which was Labor Day, both literally and figuratively ). Now that she is off at college, she has chosen to celebrate her birthday on Halloween and is planning a big Halloween party for her dorm.