Is it ok? Sure but it will take longer to achieve what could be done in less time. Complex carbs cannot be stored as glycogen as quickly as simple carbs so there is a limit to how much you can utilize in a specific time period. High GI foods can be stored much faster so you can shuttle more of them into your muscle in less time.
If your carb-up is only one day then I'd say using only complex carbs would be selling yourself short. It'd be nearly impossible to completely fill your glycogen stores in that time. If you want to play it safe then start out with the higher GI foods and as the day progresses start switching to complex kinds.
Just remember if your glycogen stores are empty then it doesn't matter what kind of sugary stuff you eat, they will go straight to your muscles and not to fat.
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