It always seems to be raining at the 'Sunshine' Coast. In its defence generally the storms are usually at night time. We had a recent trip to Australia Zoo and it rained nearly all day. We had a really good time regardless as the Zoo like many other Coast attractions cater for rainy days.
Camping/Beach/Outdoor Gear: Bring an umbrella or raincoat
Very hot in summer so bring cool clothes. Even in Winter jeans and a jumper are as tough as you need to go. We have walked in the ocean in June and July - probably not everyone's cup of tea at that time of the year though.
Toiletries and Medical Supplies: Lots of suncream if you are outside and a big hat but that said you can buy that stuff everywhere and as cheap or expensive as you want.