Here We Go Again!! Post Office raising rates!!

The price of regular mail is staying at 34 cents, but rates are going up on everything else. Instead of an addition ounce being 21 cents, it's going to 23 cents. Luckily the proposed cancellation of Saturday delivery did not go through. At this rate, though, the Post Office is going to start raising rates every month. The new rates start July 1. My wedding is late Sept. and because I was going to be out of town for several weeks in August, I was going to send the invites out just after July 4 so I could hopefully get responses back before I leave ... now I'm thinking I should send them Jun. 30 to avoid the rate hike. Is that too soon??