Congrats about all her progress with her tooth, and reading and writing - it is amazing to be see it all isn't it?
Wow, you have huge ideas for her birthday/party! I understand the excitement
But if it is causing you such stress financially, maybe just go to the beach as it doesn't cost anything?
I always set my standards for my Son's bday party too high also, and in the end have discovered that they don't need a massive party with tonnes of things to do, they really are just happy playing with each other. My Son barely remembers being 5, and he is only now 7yo
I have stressed myself out majorly every single year with his parties, whereas he is such an easy going kid, in a way, it was ME that I throwing the party for, if that makes sense?
Can you ask her what she would like? Which aspects are you struggling to afford?
Also, if you act disappointed with what you provide her, then she will think it is all bad. If you act excited, and talk it up, whatever it is, she can get caught up in that and be happy, regardless 