I'm so sorry! Truly sorry.
I think I would make my decision based on what you think her life will be like when you're gone. I'm not trying to be morose, but that's how I would decide. The person who will be caring for her will be in charge of birthdays at that point. Will they throw her a big party or is this the last chance for one? You know what I mean?
I guess that I would also consider my legacy with her. Do you want to be a part of this party? I would. I would want myself in every photo. I would want her to remember planning every single detail with me. I think I would hire a party host, whether that is someone that comes to your house and does the makeover stuff for you or a place that you go to that does the makeover stuff for you. Either way, I would want to be involved in the festivities, not running around filling up juice cups. You know what I mean?
Also, I have a four year old and he was VERY clear on what he wanted this year. It had to be "Transformers." Since he's never seen that movie/cartoon, that meant a cake with the robots on it and party favors/decor centered around it. And he was happy! So maybe whatever theme she chooses, you can just do silly things around it.
Also, are you scrapbooking these memories for her?
I love planning my kids' and my friends' kids' parties. If you would like help coming up with ideas, just send me a message. It's not something I do for money. I just love to come up with fun ideas.
Best of luck. I'm really truly sorry that this is something that you have to worry about. I would have the same concerns in your situation though.