I live in a small golf town and the majority of our tourists are from North America, although we get a lot of British tourists too.
This week I did a couple of shifts volunteering for the local Yes campaign, and we had massive engagement from Americans and Canadians, they got it, were supportive and all took a sticker/ badge/ leaflet as a souvenir - Apart from the gentleman who told us he agreed with independence, but not the socialist way we were approaching it :)
We were pleasantly surprised to be approached by a Flemish couple, numerous parties of Catalans, and some Germans who all stated they had come to Scotland to see what was happening referendum wise, and were hoping for a big party. This was just a small town in the Highlands, they had all come well out of their way.
We spoke to as many of the English tourists as possible, a lot were wary at first, saying 'you won't want to speak to us.' Some had been told by the local Hotel manager they might not get out of the country after Friday if they hadn't taken their passports. But we pretty quickly were able to explain our position, and all intimated that they would continue to holiday in the Highlands in the future. Possibly it helps that about 50% of our volunteers are English or Welsh (area of high migration from the south.)
I've been involved in the Yes campaign for over a year. I have seen one incident of anti -English sentiment being expressed, by one person outwith any campaign group who said 'if you guys aren't going to vote yes, you shouldn't vote at all' and was called on it immediately. As I said before though, we have less Scots born campaigners than English/Welsh - so that may influence my experience.
My brother works in tourism in Skye, he has had his busiest ever summer. I don't think the referendum is going to damage tourism at all, it will almost certainly be the opposite.