Its going to be fine when you see him - much easier than you are anticipating I PROMISE! This is a great opportunity for you to be someone who is spontaneous and who is confident in going with the flow!
I'm at work and so dont have too long... so I might have this a bit muddled. He wrote that he would like to see you for lunch and gave you a certain date range? Have you replied yet? Could you reply by saying that you would love to meet up but your schedule is a bit crazy and that you will call him in a few days time when you know a bit more about your schedule. And then you can just pick up the phone and explain what times are going to suit you and then work out what works best for you both? It seems like something that old friends who are catching up might do, instead of emailing back and forward about possible times?!?
Dry Heats advice about being vague about being single is good. I'd say something like "Yeah I'm single and enjoying this time, I'm meeting heaps of new people". But totally up to you!
Yes to warm and happy and enthusiastic. I read something about how you need to make a man chase is you like you'd get a puppy to chase you. First step is to get their full attention (by being happy and warm and friendly) second step is to run away smiling over your shoulder encouraging them to chase you!
