Leaving your own wedding early???

So my wedding is tomorrow. My future mother in law has been mentioning for weeks that we should be leaving the wedding a bit early, and in my head I've always been like okay yeah we'll leave at like 10:30. Our reception is from 5:30-11 (music ends at 10:45). We're not doing a formal sendoff. Our photographer is leaving at 9 and won't even be around to take pictures of us leaving anyway. Today my future mother in law said it again: "don't forget you guys have to leave early," but then she said "probably around 9 or 9:30." She says that people won't know when to leave if we're still there. To me, even 9:30 is way too early to leave. All the pageantry stuff (cake cutting, first dance, father daughter dance) will go until 8 or 8:30 and I feel like I won't be able to actually relax and enjoy the party until all those events are over. (Sure, we'll enjoy those events, but it won't be the same as dancing with our friends and finally being able to let loose a bit.) So that's not even 2 hours after all of our events are over. Is it normal to leave your reception that early? Am I wrong in thinking we should be able to stay longer? Will people actually not feel comfortable leaving until we do?

She was also taken aback that we had arranged for a friend to drop us off at the hotel after the reception, and assumed we would be driving ourselves. If we leave as early as 9, we definitely won't be sober enough to drive, but I wouldn't want to ask a friend to leave the wedding that early. Is it expected that we don't drink?

I just hope I'm not missing the memo on some huge wedding faux pas. Would we offend or make anyone uncomfortable by staying until 10 or 10:30?