i don't think you're being weird, and i certainly don't think you should lie about it in order to wiggle out of it as some suggest. i like marda's approach. it will almost certainly feel awkward at first, but keep in mind that you're not only within your rights, you're setting a great precedent by simply clarifying everything up front. and most parents will appreciate it.
if they're offended by it, you don't WANT your kid there, right?
so don't just drop him at the door. knock, stand there confidently, smiling and assuming you'll be invited in. you almost certainly will. if not, say something like 'may i chat with you for just a few minutes? we haven't yet had a chance to get up to speed with each other's house rules and so forth, and i just want to make sure we're on the same page.'
she may be taken aback, so don't be offended if she's flustered, just keep smiling and let her gain her composure, and have a brief but comprehensive set of quick questions in mind. and sometimes it helps if you start with 'what we do' rather than 'what do you do', ie 'just so you know, we are a gun-owning family but our guns are locked in a safe and the key is well out of reach. what's your gun policy?' or 'our pool has a locked gate around it but i still don't let the kids this age out in the backyard without me, just in case. is there a pool here?' or 'dallas can have an hour of video games per day, but we're fairly tight about which ones he can play. were you planning to have them play video games today or will they be outside?'
i also think it's okay to ask to stay, and their response will tell you volumes. again, if she's a little flustered i wouldn't hold it against her, but if she's pissy or resentful, well, that will make for an awkward few minutes, but again it will give you a clear answer on any further time spent with them.
but i'll bet it's fine. if she's planning on a playdate anyway, you saying 'i'm happy to have a chance to get to know you. i've brought some irish soda bread, and was hoping we could chat over a cup of coffee while the boys play.' if that feels too much like an ambush, call her beforehand with 'dallas can be a little shy in a new place. would it be okay if i hang out with you while they play a time or two while he gets comfortable there?'
however you choose to handle it, bee, don't worry about being out of line for taking a firm stance.
khairete
S.