We'll be taken our yet unborn baby to DLP next March - baby will be about 7 months. And we're not taking him 'for him', he won't remember a thing - we're going for our DD who will be 6 by then.
However, I disagree slightly with the poster above in two aspects - if you want to go, go. He won't remember any of it, but you might end up with some lovely photos to entice him with for when he gets older and you can get him excited about a more 'grown up big boy' trip. It's up to you that one completely! But yes, it would be a trip for you not him. We're going in March because it works for us with school holidays, our friend is coming for the first time too, and it may be one of the last trips we can do with DD with her being free! There's not many under 12 free offers around! (Plus my husband is perfectly happy to use the baby as an excuse not to go on rides!! lol)
The other aspect is the age. We first took DD when she was 2 1/2 years old and she remembered and enjoyed every detail! Granted, maybe it depends on the child, but after that trip (two days in the park only) we didn't go back until her 4th birthday, and in between she would often speak about DLP and all the things she did and would want to do again! So I'd say 2 1/2 could be a good age for a first visit!
Hope that helps!
C x