I usually take mine off for major coasters only (like Hulk). From others experiences it seems they are likely to stay on but I just get nervous I might lost them. I essentially fold them and grip the temples and it works fine.
If it's a possibility for you, I would recommend getting daily contacts to wear for theme parks and water parks (water parks are especially annoying with glasses). This makes it so you don't have to worry about them at all and it really helps with 3d effects on rides and shows. I usually take my glasses with me to the park and leave them in the car. Then just put in the contacts when i head in and remove them when we leave and go back to my glasses.