How do I use a Laptop in a concert?

I really need help!

I have some sound effects I need to play during a concert with my band, and they are all in my notebook. Also, I have a keyboard software I use to simulate a keyboard. But I don't know how to amplify the sound from the notebook so that the crowd can hear! It has to be really loud, we will play for 500 people. How can I do it?

My notebook does not have a line out, only headphones and mic in jacks. I thought I could use a 3.5mm-1/4" TSR cable from the headphones input to the mixer, but I imagined the volume would be too low. Would there be risk in doing that?
Alternatively, could I use a 3.5mm-1/4" TSR cable to connect the notebook to a Direct Box (I'm buying a Behringer DI8000) and from that to the mixer? i'm figuring it would amplify the signal, but would there be no risk of damaging the computer?

If anyone knows any of this, please help! If you have another solution, please let me know!

Thanks,

John