I would definitely go before they turn 3 - with twins that's a LOT of money you can save compared to waiting until 4! So, I guess I would pick a time of year that works well for the family and go at that time during the year the twins are 2. Besides being free admission, it's free food at any buffet and you can have the family of 5 in any room legally.
I agree that if you can only afford to go once or twice in a child's life it makes sense to wait until they are old enough to be able to ride everything, but for *my* favorite trip, I think it will be hard to top watching my little toddler's eyes light up at everything that was so new and exciting to him![]()
It's not about the money - we can afford to go often. It's just that I did want my DD to remember the trip and also did not want to bring her to a magical place where at every turn she was confronted with the fact that she was not tall enough to ride a lot of things. Her height was a huge factor in waiting as well....