I am so aggressive when it comes to companies/people on the phone, etc., and even rude customer service people at the store.
But, I am awful at these types of things and almost a coward, which doesn't correspond at all to my other personality. I don't know if you made these promises when drunk, but I did something similar which I kind of regret. I offered to share my office (which I'm never, ever in) with someone else. I didn't even remember doing that until she asked if "the offer was still good" in last mid-summer. I immediately hated myself but then I realized I'm seldom, if ever, in my office. I simply told her (through text) that she could use it after 1 p.m. (when I'm gone). It's worked out fine.
If I were you, I'd simply send a nice text message, with some smiley faces, lols, whatever you need to do and blame it mostly on insurance and liability.
Of course, you could take the direct and rather harsh position that some are advocating, but in the end, the same results will be achieved. Instead of stewing over this, send the message soon-ish and be done with it. They will probably like to save face as well.
The have abused the invitation and they should know that. If someone offered me something like that, I might go over once a week, but even then, I would feel very odd unless we were related or BFFs. Just too weird.