Ok, I have no idea how I missed this thread before - but here I am now! lol
I didn't read all of the posts, so I apologize if this is repeatative ... but here are my thoughts.
1) I think a lunch and dinner type thing might be overkill - at least it would be to me. Sure you could have the lunch, and if people want to hang out after, cool, but it doesn't need to be a fancy, extravagent affair. Go to the bars!
1) If they're willing to pay for a rehearsal dinner (and I agree that one is not needed) it would seem that this dinner would likely cost the same, if not more, than a lunch the day of the wedding. No? So, say you don't want the rehearsal, but can she pay for the lunch instead? If she needs proof, go get a quote where you'd have the rehearsal, and say here is what it would cost ... my hunch is that it would be the same or more than the lunch.
3) I'd say do your 11am wedding, then have a lunch afterwards. This lunch should be funded by the $5K + "rehearsal dinner" funds ... that should easily cover it - right?
4) If you really feel the need to have something organized afterwards, just have some drinks, or maybe just dessert at the house afterwards. Wedding cakes don't have to be that expensive ... get a small, pretty cake for show and pictures, and then have the rest as SHEET CAKE! - no one will know.