How do I set boundaries and still keep things drama-free?‏

I've met a great new man, and need some advice on a tricky situation: we haven't been dating long, but things have progressed quite quickly to the point where we've been intimate twice. Both times it's been preceded by a lovely date and quality time together, which I've been ok with.

However, today he sent an email implying that our next meeting be about sex (we've had some flirty email banter around the subject, and he was more forthcoming about it today); he also sent me a long description of how busy he is this week, including that he's free one evening this week after 7:30, and fully booked over the weekend (he has his daughter most of the weekend, which is legit, but said that Friday night he "has plans" - which I'm taking to mean he has a date with someone else - we haven't talked about being exclusive, and I'm trying hard not to raise the issue as I think it would lead to him pulling back).

Anyway, my old self would have suggested that he come by on his one free night this week, even if it means we're essentially just getting together for sex; but the new me recognizes that this would mean I'm accepting having a relationship with him that's primarily about sex, which isn't what I want ultimately ...

But, not having much experience with setting this kind of boundary, I'm not sure how to do it. If I turn him down this week, it means not seeing each other until at least next week/weekend (and, possibly, falling off his radar); if I don't, then I'm letting him know that I'm ok with a mainly physical relationship.

I know I need to set a boundary. How do I do this without making a big deal of it? Do I say to him outright that I don't want a primarily physical relationship with him? Or do I just say that I'm busy this week and ask for a raincheck, without making an issue of it one way or another? Or maybe I say that it's too bad that he's booked on Friday, since I have the evening free - for now?

I want to give him space to pursue me so I haven't been calling, and only send emails if he sends one first, and when we're together I do my best to be "in the moment" and not project or hint at an imagined future ...

Any thoughts, advice, help, insight are appreciated!!

Some background on the guy for anyone interested:

-He's recently separated

-We met online; last week he took his profile down, a few days after we had sex for the first time - I didn't ask him about it so don't know why he decided to do that

-He has told me (after I asked) that he's meeting other women (though I suspect he's not sleeping with anyone else, but don't know this for sure)

-He says he's not looking for anything serious, but *is* looking for more than just sex, and to connect with one person (I'm not sure what that means exactly for him; I'm guessing he's using the "nothing serious" line as an easy out if he decides to back off)

-The connection and chemistry are great - we have really good conversations, I feel very comfortable, safe and at ease with him, in a way I rarely have - but am really trying hard not to make more of it than it is!