I think you are on the right track about simply replying to say his help would be great this weekend. You're right about keeping calm and not showing excitement. In your mind you have to say H is doing me a favour and not try to read too much more into it. Perhaps having a bbq might be a bit much because as you don't eat meat it shows you had an expectation that he would stay by having meat on hand. However, I'd have a cold drink on hand and some nibblies which you just happen to keep in the fridge/cupboard. You can always pop out for a bite to eat or to grab some meat if the opportunity arises.
The emails are exciting and a real breakthrough and certainly his visit is a great move. From my own experience don't stuff it up as I so often did by being overly anxious/eager. Be cool and remember no expectations. He's helping you. That's awesome. Take it as a real positive and try not to read ulterior motives into it. Let him feel his way back quietly, slowly and calmly.
