Getting into US with convictions

Hi, can you help revelal the truth on this one please?

I live in New Zealand and have 2 DUI convictions as well as a cannibis use conviction. All when I was in my teens over 20 years ago, nothing since.

For a week's holiday in the US should I declare these? I know you're supposed to get special permission but how would the US know about these convictions?

I just want a family holiday without the hassle.

Anyone's who's done this could help.

Thanks

Babbles