Good for you for going ahead with birthday party! Try to maintain a normal life (if possible). One thing I felt during treatment was my lost of identity. I felt like people saw me as "Laurie with CANCER". I was still the same person I was before.

Ask for help with party and during treatment. It is OK not to be superwomen, you will have only so much energy, so prioritize what is important in your life and the rest will take care of itself. I considered myself a strong independent women and was one of the hardest thing was for me to ask for help. I still tried to do everything myself and it was exhausting.

If you can afford it, get a maid service while going thru treatment, accept offers of meals, babysitting, etc... You will need rest.

You might want to check Mayo website for dealing with Cancer & Cancer treatment symptoms:
https://cancersymptoms.mayoclinic.org/
Laurie