It was a it anti-climactic after Disney. Really depends on how much your child loves Lego. If they are a Lego lover I would say go, if they are Luke warm then I would say not to bother.
Honestly I really think you would get more bang for your back by spending minimum three days but four even better at Disney. There is a lot to see and a lot to take in, and if you only go for two days you will be missing a lot. Honestly you could go all five and still not have seen / done everything.
Have you hammered out dates yet, that will also affect how much you can accomplish while at disney.