50th Birthday Help

My dad turns 50 in September. I am throwing him a surprise party in August. I have already booked the hall, the DJ, and thought about food. We are going to have chicken, potatoes, spagetti, salad and cake. For his gift i am having a video of old pictures and film made. My problem is, What about decorations (the theme is fish), and what to do during the party. I am also making candy bar wrappers as pary favors. Can anyone help? THere will be about 60 people.
Thank you
Sara iwuvwoo@excite.com