We love going in January. MLK weekend is busy, but if you can avoid MK for those 3 days you'll find that the crowds at the other parks aren't too bad. And then crowds are very low during the weeks before/after MLK weekend, so if you go at that time, plan your MK days for those days and then plan your resort day for one of the days over the long weekend, since I think the majority of park visitors for MLK are locals. So do some resort hopping or book some nice resort ADRs, lounge by the pool and do your laundry, visit DTD, spend half-days at AK or HS. It's totally do-able and you can absolutely maximize your park time if you plan right.