Hello Jax.
I am sorry you are getting stressed about this party. Would it be so wrong to just see your mother sooner and take the present and spend some time alone with your mother possibly take some take out and enjoy the day with your mother. And then when someone asks why you didnt celebrate your mothers birthday, tell them you are starting to enjoy the rest of the time your mother has left when she has a birthday by enjoying time alone with your mother. Then having to get stressed will be replaced by something you will ejoy reliving after your mother is no longer available to have time alone with in the future. Take care I hope the best for you. Soidhonia