Hello, Jenny)
Well, your essay is not very distinct( I understand that to make a good answer in 100 word limit is quite hellish, never tried myself) , try adding more personal strokes, try to show what makes you different from others, maybe, your special approach, mindset, because everyone who works at fundraisers smile and promote.
sick childrenwith and their families
Ronald McDonald House Charities (RMJC)
just write RMJC, don't waste words on full titles, anyway the McDonald's guys will understand
Working at McDonalds has allowed me to make a difference by supporting charities and organizations
well this is too obvious, I mean don't waste words on sentences like this, dig immediately into more personal stuff.