Can you do both (Minute Waltz and Invention no. 1) or would that be too much for you? If not, I'd finish no. 1 since it's required anyways, then work on finishing the Minute Waltz. I've played both and I found the Invention easier than the waltz.
I stopped the Waltz, and am still doing No 1. I think it is only hard since I fail to understand it though the fingering is easy (like it was taken out of Hanon LOL). I like No. 2 since it is slow and lyrical. But it is still too hard.
lol
just wait until you play FI...
btw have you considered fur elise? 
LOL, is FI very repetitive?
I totally forgot about Fur Elise! Haven't heard that in a while. Since I don't like most classical era, I haven't thought of Beethoven except for sonatas. I wonder is Fur Elise is really Grade 3, or if the piece I have is simplified. I'd want to play the real thing.
I really enjoy his preludes. I haven't really played many of them, or much Chopin at all though.
Favourite prelude is No. 15, and I also like Nocturne in D Flat. They are probably overplayed but really, who cares?*
I don't have my preludes book; I lent it (my mistake). We seem to like Chopin in D-flat much, don't we? I love Raindrop Prelude, but I don't think I'd be able to do it justice. And I might not be able to perform such a long piece in a students' recital. I can imagine half the audience sleeping.

The nocturne looks scary. Is this really difficult?