OK, I'm in transit so not able to help much.
For random non repeating order, you need a shuffle.
There are many ways, here's a thread I found maybe a better one will turn up
I like the Fisher Yates algorithm, but scrambling 13 things can be done with simple techniques you can see right away how they work.
L8R - here comes the beach. Spectacular weather, gentle breezes, calm sea.
a7