Alot of cane toads are VERY skiddish, mine still won't eat if they know I'm there. What I often do is feed them while they are inside a log or hide in a direction where they can't see me. I'll drop a meal worm, cricket or earth worm into the tank with a pair of tongs and they'll come out of the hide for a second to gobble it up.

Good luck, it just takes perseverance.