Take a look at youdomain.com/summary.php - it does what you are asking for except for "the first line" portion. By design it'll show three posts and titles in each blog that is publicly available. You can change it to show one post per blog fairly easily - a minor bit of editing the file.

you can just create a blog that aggregates all the other blogs, and use that one blog on the front page. then skin the template for that blog only, whittling it down to just display blog name, post title, etc...

as far as summarizing goes, you'd have to train your family to use the !M button.

The only problem with aggregating is you will get the most recent posts across all blogs, which can easily leave out posts from infrequently used blogs. So if you want X posts from EACH blog you have to go with summary.php. On the other hand if you don't care if infrequently posted blogs fall off the main page then aggregation is the easier way to go.