Sophie's mum here! Welcome to the wonderful world of chicken keeping! I'm still a novice myself, but I'll be brutally honest - if you like a perfectly weeded and pristine lawn, forget it, as for slug pellets, you won't need them cos the chooks will destroy the vulnerable plants faster than any slug ever could (plus they'll also eat the slugs) I've been away for a couple of weeks and my Dad has taken care of the chickens, and the kids let them out for their normal foray into the garden.
I got back to find that the bluebells had been decimated, the gravelled alpine area on the patio is now a kind of gravel pit (minus alpines) and in their own haphazard way the chooks had helpfully attempted to earth up my emerging potatoes :-)
Having said that, I wouldn't be without them, and I wouldn't risk putting down potentially harmful chemicals, have fun!