Create a New Post with the Subject line containing - Event Date, Event Name. Feel free to write anything in the post itself.
If your photos are already online such as on your Google Account or on Facebook, you can just post the URL to the share link (either to the specific album or to the actual photos themselves).
Of if you need to send over the actual photo, you can just attach them in your post. Go to Attachments Tab (right after the text entry box) and then click on 'Add files'. Add up to 10 files per post. If you have more than 10 files that you want to share, just post your initial 10 files and then reply to your own post and added in the other photo attachments.