We also go to Busselton a few times a year and either stay at Beachlands cp or Mandalay cp. Both these parks are top notch. They also have the prices to match. Mandalay is directly across from the beach and Beachlands is one street back. Both have great ammenties and the sites can be a bit small in size. Best to avoid in peak summer holiday periods. Both are great for kids. Both have pools and big jumping pillows. They even give you a helping hand when reversing in.
http://www.beachlandsresort.com.au/
http://www.mandalayresort.com.au/
wizzer
http://www.beachlandsresort.com.au/
http://www.mandalayresort.com.au/
wizzer