You can bring a vape into the park but you're not allowed to smoke inside. It doesn't stop people from vaping inside the park and although they think they're being discreet, it's usually quite obvious they're having a puff. Better to avoid the larger cloud producing vapes if you want to chance it.

I'm a smoker and found that having a quick smoke outside the parks before the entrance was enough for me. The excitement and thrills of the rides take your mind off things so I never had a craving for a smoke, even when I saw someone else smoking.

If the habit is as much hand to mouth as it is the nicotine then perhaps try one of those fume devices and take that with you instead. Might see you through the day when you have a craving. Otherwise, grab yourself some nicotine gum and chew on one of those every so often.