OP, II really love the chocolate cross idea-- my mom's best friend owned a chocolate shop, so she did an assortment of Catholic chocolates for my First Holy Communion (way back in the day!) I think there were crosses, mini churches...some others, I believe. Pretty fuzzy on the details. You can never go wrong with edible favors!
However, I have some much younger cousins who both received Communion about three or four years ago. One family dressed up their daughter in her dress/veil a couple weeks before the day and took a picture. The favor was that picture (wallet size) in a small silver frame-- I know the frames were actually wedding seat assignment frames that she got in bulk on a discount favors website. Not sure how much they were, but I've seen similar ones for $1 on websites.
My other cousin is half Colombian and her communion was a huge deal. They had these custom-made mini chairs with a Bible resting on the chair-- and a personalized ribbon with the girl's name and the date. They were made out of beads and were clearly handmade. I cannot imagine how much they were.
So, to answer the PP who had never heard of Communion favors-- I think it depends on the family, culture etc. We have favors at all "big" parties-- just the way we do things. However, I don't think anyone would think anything of it if you didn't. Especially if you were only having guests over for brunch. My, my brother's, those two girls, and all other relatives had late afternoon parties of 50+ guests.