Always book ahead for any sit down restaurant that allows you to book ahead. Period. You may be fine, it may be the off season, but you never know. Just play it safe and always book ahead. The more ahead, the better.
Our revels now are ended. These our actors, As I foretold you, were all spirits and Are melted into air, into thin air: And, like the baseless fabric of this vision, The cloud-capp'd towers, the gorgeous palaces, The solemn temples, the great globe itself, Yea, all which it inherit, shall dissolve And, like this insubstantial pageant faded, Leave not a rack behind. We are such stuff As dreams are made on, and our little life Is rounded with a sleep. mycroft16 on Twitter
Absolutely book ahead. Not only that, but show up about 15-20 minutes prior to your scheduled reservation. They seem to call people down the stairs in the order they arrived. You'll get a head start if you're there early.
The food is surprisingly good for DLR (not great, and it's overpriced, but it's no Village Haus either). My kids love it there.
I'm another one that says use Disney Dining to make your Priority Seating arrangements for ANY restaurant that they offer it for. Why waste the time standing in line or worse yet (like so often with the Blue Bayou) be turned away and told to come back another day?
Though if you are looking to enjoy it this w/e, you might be out of luck for P-S arrangements. They do "sell out".