Good Luck! I threw my dad a huge suprise party this past year for his 60th. He isn't much of the party type himself. He never ever wanted anything either, "just your love" is the kind of guy he was...
We did a hawaiian theme and it was a blast! There is so much you can do with it! It doesn't matter what time of year either! Just as long as it isn't FREEZING out is the only time I wouldn't do this one. But I bet in November you'd be fine!
We did food with Pinapple, and Mango Salsa, and all kinds of fun stuff. People had the most fun with the SPAM stuff. SPAM is huge in Hawaii so it fit well into everything.
US Toys in Plano is a great place to shop as well but get creative with things you may already have. Try and look at things in new ways! Decorate with bright colored beach towels, whether they are just stripes or have a hawaiian print. Get every day rope and use it, buckets for ice... You'd be suprised what you already have to use and can go perfect for FREE!
Have everyone dress the part and they become part of the decorations. Make it a contest with a prize for the best dressed so they really get into it! Have a Hawaiian shirt at the party waiting for your dad.
We did it at our church. He just thought he was going to someone else's baby or wedding shower I think I told him, can't remember, but that was actually the easy part...
Let me know if you need more help and like this idea! :o) Good luck!
~T.~