This is more of a personal question you will have to answer yourself but I can definitely help you brainstorm!!
You could write about an Easter egg hunt or dyeing egg shells different colours.
It could go like this:
Dear [name of your friend],
For Easter Day I will celebrate by waking up and doing an Easter egg hunt, I will hopefully find [favourite chocolate] eggs because they’re my favourite type and I like how they taste, I hope you wake up and find some of your favourite chocolates, I also plan to spend time with my family because I think that’s super important, I was also going to do some arts and crafts and draw some Easter themed drawings. I’m really excited and I hope you have a good Easter as well!
Love [your name]