I'm sorry to say that's so badly out of focus its next to impossible to be sure which caterpillar it is - can't even tell whether its hairy or not, can you get a better picture?

They are hairy couldn't get another picture as my 3 year old is in love with them black and yellow stripped

Well then its not possible to identify them - the link below shows various caterpillars, maybe you can find one like yours there. The buff tip moth one might be it, but, and its a big but, if you've got hundreds of them, they're likely not anything good, so it won't just be a couple of moth caterpillars, and hundreds of them will devour various plants

http://www.fotolibra.com/gallery/602556/hairy-caterpillars/like/

I'm not sure why your 3-year-old being in love with them is preventing you from taking a better photo...?

Use the macro setting on your camera (it's the button with the flower symbol) to get a clear close-up.

Hi, from your description, they're probably from the cabbage white butterfly, go out 1 night, after your 3 year old has gone to bed, and get rid of them, tell your 3 year old that they went away overnight, they will soon be forgotten, Derek.