I couldn't help but notice the contrast between this and the other thread asking about bringing a baby to Disneyland. You're actually asking if it's okay for you to go without kids. I love you!!
Heck yeah it's okay to go without kids! I know that there's this big cliche that "Disneyland is for kids," but it's not actually true. Nowhere in the dedication of Disneyland does it say that the park is supposed to be exclusively for kids. Furthermore, in all the conversations I've had with people who insist on bringing infants and toddlers to Disneyland, it becomes quickly apparent that despite trying to justify themselves with the statement "Disneyland is for kids," they're really going because they want to go and they're not about to let their own kids stop them. And then big kicker, the corollary of the statement "Disneyland is for kids": no one is actually obligated to bring their kids to Disneyland. My parents never took me, neither did my fiancee's, nor a lot of people I know. I'm sure it's great to share it with them (and I think you're doing awesome by waiting at least two more years, so they'll come within spitting distance of remembering it as something special), but you're not a bad parent if you don't take them.
So yeah, you're not a bad parent if you don't bring your kids to Disneyland, Disney is not for kids exclusively, and if you want to go because you want to go, then ditch the kids and take a getaway for just you two. Don't feel guilty about it at all!