we're creating promotional offers. promos consist of n lines, and they are combined by AND/OR using postfix

eg:
1: buy 2 coke products for 1$ each
2: buy 2 pepsi products for 1$ each
3: buy between 1 and 3 water products for 1$ each

we display all AND like this (1 AND 2 AND 3):
Choose ALL:
buy 2 coke products for 1$ each
buy 2 pepsi products for 1$ each
buy between 1 and 3 water products for 1$ each

we display all OR like this (1 OR 2 OR 3):
Choose ONE:
buy 2 coke products for 1$ each
buy 2 pepsi products for 1$ each
buy between 1 and 3 water products for 1$ each

the challenge is how to display mixed and/or. eg: 1 AND (2 OR (3 AND 4))

for small promos with 3 lines it's pretty simple. but how do i handle it in the generic case? our users are non-technical, so we can't really give them the formulas / postfix / tree and expect them to understand.

at the moment we're converting them into multiple promotions so that each promotion is either all AND or all OR. i dont really wanna use a wizard and choose 2 lines at a time until it's satisfied. is there a way to show it intuitively to non-technical users?