Nice to see another Dad here with us!
I have a 3 (almost 4) yr. old who loves
Dora and Diego. Both boys and girls love them.
Blues Clues,
Bob the Builder, Fire Trucks, Army Men, bike theme, race car theme, motorcycles, trucks like dump trucks, cement mixers...ect.
One show that my daughter absolutely loves is
Big Foot Presents Meteor and the Mighty Montster Trucks show.
Another really easy party theme would be to use all primary colors everywhere....a few balloons and music.
3yr. olds get bored easily. There main "wants" is to open gifts and to play! (maybe cake too.

). Don't stress yourself over this party! Have fun....they are only that small for a little while!
I would recommend buying a cupcake for the little one to use to blow out the candles and to eat. You would not believe the number of people who have told me that they refuse to eat a piece of cake after a young one has "blown" out (I should say spit on) the candles on their cake. My husband and I watched this very thing happen when my nephew turned 2 and my DH will never forget it.
I have to agree with the Dollar Tree for great accessories like small gifts like coloring books, story books, cars, and plates, napkins decorations to go with your party theme or favorite color.
I know that a lot of people purchase things from the Oriental Trading Company online. I can't speak from experience, though.
Once you decide what style or theme you are going to use, if you would like more ideas, please let us know!
I hope that you will join us in other areas of the forums too. We are always in need of a Dad's opinion around here!
Tami