they're not coming to judge you or your home - it's a chance for your DS to meet his teacher again before he starts (I'm guessing he may have had a few visits at the nursery before the summer holidays - if so it's a long time for a pre-school child so probably won't remember them much - refreshed his memory in a place they feel "safe"). Also a chance for you to air any concerns.
nope no opportunity for him to visit nursery. We went to a parents only meeting then they do home visit then he starts. Which is why I dont fall for the whole 'breaking them in gently, meeting teacher in a quiet environment', he hasnt met her in any environment
I always enjoyed doing the home visits when I was a nursery teacher. It gave me a lot of info to help settle the child in in the first few days. Just having someone talk about familiar things to them can help them feel more settled.
Also, from the other side, when DS started nursery if it wasn't for ther home visit first, they might not have believed that he could actually talk, given that he was selectively mute! Thankfully he chatted away at home so they knew it was selective mutism.