It was a half day park for me, and I spend a shocking amount of time and money on
LEGO. Keep in mind that I’m not traveling with kids, so I move FAST. I’d say a day would be swell, especially if you can skip the water stuff, but two might be useful if the kids are super fans.
Much like Universal, LL has a ton of photo opps, but the content behind them can be a little lacking. And the employees are employees, not cast members.