I use my Brittany for ferreting, now that I've given up the Falconry thing, she loves it! She doesn't catch many but she tries her hardest. She'll sit and stare at a warren when the ferrets are down, though sometimes, once the whippet has launced himself at a bunny, she'll stand and watch as if to say "f**k it, he'll get it, I'll wait for the next one"!
Give it a go, don't expect loads of bunnies, but if the dogs enjoy it, then it's worth it.
Ferret