Cirno: Halflink Monk 1/Soulknife 1/CW Samurai 1.
I may or may not be kidding.
Reisen is a Marksman. Pick up Expanded Knowledge for Id Insinutation and the like as needed. Are there stats for rabbits anywhere? If there are, she can be an Anthropomorphic one.
Sakuya (and Youmu) I'd personally stat as a Swiftblade. Use the capstone ability for lots of Time Stop. If you can get 9th-level spells and Swiftblade 10, reflavor Maw of Chaos to lots and lots of daggers. Youmu could be a lower-level Swiftblade with levels in Crusader and JPM as well. In fact, Youmu should be below ECL 20, since she's half-baked.
Also add Martial Study feats and Diamond Mind Rings liberally so they can pick up Time Stands Still, which both use frequently in their spellcards. Soul Sculpture is essentially Time Stands Still plus full attacks with dual daggers.
Yukari is an Elan Nomad... whom an Efreeti and a Sarrukh owed a favor.