Which charity donation page for multiple charities?

In two months' time, and to mark my 50th birthday, I am cycling from Land's End to John O'Groats in 10 days. I'm self funding the trip, however I want to set up a charity donations page, where I'd like to split any donations 50/50 between two cancer charities, Cancer Research, and Young Lives vs. Cancer.

From what I can see, GiveWheel seems to be a decent option (Just Giving doesn't allow a 50/50 split from what I can see).

I've got very little experience of this area, so any advice around which platform is best would be gratefully received. Thanks!