Just don't do anything with the leaves! My parents used to have some rhubarb in the garden when I was young, and I had it drummed into me how poisonous the leaves were (not that I was the sort to go around eating random plants). Looks like "a 65 kg adult would need to eat 4 to 8 kg (9 to 18 lbs) [of leaves] to obtain a lethal dose"[0], although I guess you could still get pretty ill with much less.
[0] https://en.wikipedia.org/wiki/Rhubarb