Hi, thanks for joining in. Hopefully you'll find what I write interesting as we are coming from the same experience as you.
First off 5-night vs 7-night, while DW especially wished the cruise could've been a little longer, I don't at all regret not paying twice the price for two more days. I wish we could have spent a few more days on land after the cruise, but flight costs wouldn't let us. I think you'll be fine.
As far as alcohol goes, Disney allows you as much alcohol as you carry on. Note the term "Carry On" - you can't pack it in your checked luggage, it has to be in your Carry-on. We had 10 bottles total between 4 people. 4 bottles of hard liquor, 4 1.5-liter bottles of wine, and two 750-ml bottles of wine.
They charge a $20 corkage fee per bottle of wine at the restaurants. We saved extra $$ here by buying 1.5 liter bottles of wine for the 4 of us at the table, but we are not real finicky with our wine either. I am not sure how much you really save doing this - someone else pointed out that the wine package - for $159 for the trip, gives you one bottle of wine per night. In our case, we probably spent about that, but got a 1.5 liter bottle instead of the 750 ml bottle. We had 750 ml bottles for Palo night, so overall, we spend $120 on the corkage fees + another ~$100 on the wine, which would've been less than the $159 x 2 = $320 Disney would've charged us. (They actually forgot to charge the corkage fee one night - so it was actually less.)
As far as the rest of the cruise, while you can't have your alcohol obvious out on deck, DW and I brought those metal water flasks, and added the whiskey/bailey's in our room, and then topped them off with ice / soda at the soda machine. I definitely got my money's worth out of those two bottles of alcohol, because drinks on deck were $7-$12 each. You could also buy beer stein which gave you discount refills on the beer if that's your choice.