I've got a similar situation in my classes and I found out that what you really need is patience and time for you and your students
There are plenty of activities and games on MES site, you could also listen to some podcasts: http://www.eslteachertalk.com/
. I found them very useful. Find the ones that you like or seem ok for you. If you like them your students will like them, too.
Let them sing songs, draw and colour, tell them stories!!! Give everybody plenty of time to listen first before they speak. To tell stories you can use puppets or, what is more interesting and creative for kids: Cuisenaire Rods. If you don't know them, let me know, I can post some activities on using them. It's a really great yet simple tool to teach English.
Why do you need patience? Because if you've got a mixed-ability class it's really harder. When you present target language some students may already know it and they seem bored: engage them by being a little bit like an actor or let them help you - this can be a great time for teaching them how to help each other. When they finish earlier be prepared to have something extra for them. My kids love Hidden Pictures. You'll find them here: http://www.highlightskids.com/GamesandG ... rchive.asp
or just go to www.highlightskids.com
and look for Hidden Pictures. There are plenty of them to download for free.
I am sure that after some time you will see great results, because your students will learn not only from you but also from each other.