I think it comes down to what you have time for. I think its something once you commit to it you should stick it out, so make sure you can give it your best. If you have to many other commitments and other things may suffer because of it, I would turn it down. If you think you can handle it with everything else then go for it.
"Until one has loved an animal, part of one's soul remains unawakened..."
- Anatole France