Your problem is that you've chosen an App that has no upgrade path from iPhoto. So, you have to accept the consequences of that and make your choice:
1. Start over from scratch. Export all your masters to the Finder, import them to LR.
2. Pick up from where you finished. Export the edited versions.
3. Export both and have duplicates in your LR Library.
The one option you don't have: you can't run LR on the iPhoto Library or vice versa.
If you chose Aperture instead of LR then you have a simple migration.
Sorry that the only way is not the way you want - but it is what it is - LR can not use the iPhoto library - it does the same thing as iPhoto in a different way and there is no compatibablity between them
Many people find Aperature as good or better than LR and it does share the iPhoto library so you lose nothing and duplicate nothing going ot it - maybe you should look at it
The metadata will transfer if you export it correctly
As to editing you have two choices - export the current version which is the edited version -- or export the original version which will be exactly what you imported
Generally when you move to LR you are doing it because you have RAW photos and want more editing control - if you export the currect version you do not get the RAW
"If" I were to export all my photos to LR
If you're moving to LR then there is no "if", it's not a choice...
This User Tip
has details of the options in the Export dialogue.
So, yes you can export will all the metadata - but again, you have to choose. Exporting Originals will get just that - the original file, with the metadata the original file had. But that won't have any metadata you added in iPhoto - like keywords, titles, faces and places. To get those you need to export to tiff or jpeg, as described in the linked article.
Note: there is no way to move Faces. There is simply no agreed system to share that data among any photo apps. Best you can do for those is keyword, and use that to help you start doing the same process in the new app.
Actually? There is a way to manipulate iPhoto directories directly in Lightroom.
1.) Create a new Lightroom catalog ready for import. Save it wherever you need it.
2.) Open your copy of iPhoto. Select a photo. Go to File>Reveal in Finder>Original or Modified, whichever you'd prefer.
3.) Finder will show the file in a child folder (under the Masters folder). You can then use Finder to navigate to any folder within Masters.
4.) Drag and drop any folder you'd prefer into your new Catalog and import the pictures.
Note that your work in iPhoto will not be saved if you select your original files. If for whatever reason you'd like to avoid exporting your originals from iPhoto, however, it is possible to use Lightroom to navigate any folder within iPhoto - as long as you use iPhoto itself first to reveal the file structure in Finder.
I've been doing this for months, if not years, and haven't ever had any problem with my Library. I do go in and manually delete thumbnails from my iPhoto Library for any photos corresponding with original files I've moved or deleted using Lightroom.
Have heard of others whose Libraries were corrupted and who didn't see thumbnails for hundreds of original files which were still intact in their Masters folders - photos iPhoto would skip if you were to try to directly export them. Personally, I'd rather corrupt my iPhoto library than lose irreplaceable original photographs. But, to each his/her own.