My Mom and I took advantage of the free dining last year, and the crowds were not bad. I think the bigger difference is that the restaurants may be busier than they normally would be with the same crowd level, since people who may not normally do many table service restaurants will be, since it's free. So, while it's usually pretty easy to wing it without ADRs during the off-season, you may want to consider making ADRs during the free dining promotion.