That's actually going to be a load to carry because of the cajon. You don't need it. You don't need hats for busking, either. Just use snare + ride cymbal and go have fun. Don't make it too complicated. I saw a great duo in NOLA every nite. Jazz guitar player with little speaker/amp and car battery for power. Played with a female drummer just snare and ride. Used brushes 90% of the time. They sounded great and made money.
Where you going to do this makes a difference. I used to go out once upon a time, and yup, the setup I saw most (I was playing guitar then,) was snare only, and snare, ride. Or buckets
Some guys took whole four pice kits out but I think they had some kind of license or something.
You definately want to be able to pick up and leave out quick