Just thought I would mention a few things I have tried in the past. Same competition and prizes
Firstly - I sent out an email version of a newsletter with the competition. I had 1 response to the competition.
Secondly - I send out the same newsletter to 300 people in hard copy - I received 50 entries.
Thirdly - I put the competition on Facebook. Received an overwhelming response - most by referral from other people entering. I end pulling it off Facebook as it was attracting people from outside my target market. These competitions are listed quickly on competition websites.
So in answer to your question - if your target market is stay at home mums then facebook is a great tool.
What exactly is your objective for the competition. Is it
a) To promote your brand to your existing client base
b) Gain new potential clients.
c) Grow the number of facebook likes your business has.
Depending on your objective will depend on your strategy.
If you are in a specialized technical industry ask for 50 words on a particular item / industry vision. This will weed out a lot. Those it doesn't you can usually pick up if they do / do not know what they are talking about.
Maybe you could post the competition on Linkedin - at least then you have a better fit for your target market.