25?! I hope she has orgasms upon command haha. Seriously though, I agree with Earl Grey if most of the stimulating will be done via tongue then id be concerned about the safety of your tongue. From my experience once you start crossing into multiple orgasms each orgasm thereafter becomes harder to accomplish then the last.

I would definitely try to get the beginning orgasms accomplished through some less intense methods and then start moving to more advanced techniques. I would also suggest have an arsenal of toys at hand haha. While I do not think 25 orgasms is really obtainable, I doubt you would need to get to that point for you to give her the best night of her life on her birthday. I drafted up a brief article on some different techniques if you want to check it out. The site is the same as my member name. Hope everything works out for you!