Does "keep it simple stupid" ring a bell? Well, KISS couldn't be more applicable to Informal Wedding Invites. Most people forget that they have to include a significant amount of information in their invites and thus proceed to cram it with useless junk. Overcrowding your invite is one of the worst things you can do. Not only may you confuse guests, but you may also encourage them to gloss over important information. Find a special quote or an excerpt from a poem, select a place for it in your invite and wrap up the process. There's no need to add additional reading material.
While addressing your potential guest in the invite, feel free to use lower diction wording - just don't exaggerate. You want to avoid using slang words or any other words that could be considered inappropriate.
Finally, don't focus too much attention on the small details. Many people spend days trying to decide whether a particular part of their informal invite needs to be capitalized or italicized. These types of things aren't important to us. If we were writing a more formal invite, we would dedicate much more attention to these smaller details.
As a final reminder, be sure to mail out your invitations several weeks prior to your wedding. You don't want to procrastinate on the wedding invitation process and have the invites mailed out a mere week before the wedding. You need to give your guests plenty of notice before you hold your wedding. Otherwise, you may find that attendance is minimal. Get working on your invites as quickly as possible to ensure that everyone on your guest list makes it to your wedding.