Just tell them that you've recently become a Jehovah's Witness and that you look forward to welcoming them into your home, so that you can preach the word of the Lord ;-)
Sorry if I made you laugh - what I meant was , whilst they are in Town you'd be happy to meet up but couldn't put them up.
They could stay at a Hotel or B&B.
I had a friend who had a couple of spare rooms and friends often wanted to stay over, she was very popular but didn't like guests. She sold up and bought a one bed apartment and now lives in glorious isolation - it's what suits you best.