That's a real "No Brainer".
Make some Black Cherry Wine with the pitted cherries and throw the rhubarb away! (*)
Not really! I would make a Rhubarb Wine but only after I had checked what the rhubarb was canned with.
If it is in a syrup then you will probably need half of the sugar required to make a wine from rhubarb that has been canned "au naturel" in its own juice.
Either way, I suggest that you search the Forum for a suitable recipe and go for it because both brews should be ready for Christmas if you start very soon and get lucky!
(*)
SWMBO and I saw some VERY cheap (8p per 340g) cans of rhubarb one day in our local Cash & Carry. We were stocking up a boat ready to retire so we bought 20 cans and stowed them away for desert. However, it was only after we had opened the very first can that we realised that the rhubarb had been canned in its own juice.
Bought in January 2003 the last can was consumed about December 2010 and my teeth are going "crinkly" at the memory!