Well, I did a google search with these terms: house warming etiquette.

First off, when you host it yourself, it is an open house, NOT a house warming. I didn't realize that. See this:
http://www.digsmagazine.com/host/host_housewarming.htm


Giving tours:

http://entertaining.about.com/cs/hol...usewarming.htm

A lot of site came up many with manu ideas and so forth. But I really didn't see an answer for your situation. (You can try the search yourself, I gave up after 5.)

You can post your question on this etiqutte board for a reply.

http://rebecca576.tripod.com/etiquet...ecca/id60.html