Let's see if I can throw my 2 cents worth into the mix:
Alcohol: You can purchase bottles of alcohol at the duty-free shop onboard & in ports but you cannot *have* them in your possession to consume until the very end of the cruise. Basically Disney will store these bottles and you'll get them back the night before the cruise ends. You can purchase alcoholic beverages all over the ship in the various bars and sometimes the wandering servers out by the pool deck. During the Captain's Reception night there will be servers wandering in the atrium area with trays of cocktails that are complimentary. You may purchase alcoholic beverages from servers pre-show in the Walt Disney Theater and during meals in the table-service restaurants. Don't forget to go to Guest Services when you board to check the schedule for Mixology and tastings. You should sign up for those because they often fill up. There's a small charge for these types of things (usually $15, give or take a bit) but you get multiple drinks so it's also a good value. You do know you can bring alcohol onboard with you, right? Yes, you can carry your own liquor, beer, wine, etc. onboard with you. The key is that you need to CARRY it onboard with you. Disney doesn't want you puting things in your checked bags because if anything breaks it's not just your belongings that can be soaked/damaged. If you bring a bottle of wine to dinner there will be a corkage fee. Otherwise, if you keep it in your room and dispense from there you have no fees associated there. This is something that is quite rare in the cruise industry and it's a great way to save a few bucks on bar tabs.
There's a family club venue on the ship called "D Lounge". In the evenings there will be things like karaoke, game shows, etc. that are for families to attend. It's like a night club kinda but it's for families. Great venue! Also, there will be movies on the Funnel Vision which could be a fun thing to do with the kiddo. Kind of like going to a drive-in movie but not. Some people will be in the pool watching the movie while others will lay in the loungers and enjoy. Honestly, how can you go wrong with a movie under the stars at sea and tons of yummy snacks right there for the taking???
I would think you'd be fine to go to the nightclubs solo! Check the daily Navigator (schedule of events) for the adult shows. Match Your Mate (like the Newlywed Game), Quest, etc. are all a lot of fun to go to. It's a great atmosphere! I'm not sure but I think there's some singles functions. Maybe ask at Guest Services. That could be a fun way to meet other cruisers sailing single.
Take your little guy to Open House on embarkation day at the nursery. You can see what it's like, talk with the staff, and introduce your son to the surroundings. Doesn't cost a thing and it's fun. Also, whenever the kids clubs are listed on the Navigator as "Open House" you can take your son and go explore! This is even for the older kids clubs including the teen's clubs. Take him and go explore! Some of the spaces are so amazing, you won't want to miss it! I'd venture to call Open House a must for all cruisers. The kids' venues are so fantastic! This is the stuff Disney is known for and does best. Why wouldn you go see????
Yes, there's a coffee bar onboard. Yes, you can get your beverages to go. I can't remember if the Magic has the coffee card but it's worth asking. I know on the Fantasy Cove Cafe has a coffee card that's buy 6 get 1 free. On a long voyage that could really pay off!
Rotational dining. When you check-in at the port your dining rotation (schedule) should be listed on your room key card. It's a series of letters in a row. A=Animator's Palate, L=Lumiere's, & C=Cariocas. That's the order of the restaurants you are scheduled for during the cruise. Your table number will be on there as well as your dining time. Go to your first restaurant on your first night and meet your serving team. Your serving team will be yours for every main dining room dinner for the entire cruise. You'll get to know your serving team and they'll get to know you. By the end of the voyage they'll be like family. On our first cruise, the first thing we did was tell our main server that it was our first cruise and didn't know anything. We asked for help figuring things out. He helped us with all kinds of fabulous information for the duration of our cruise which was wonderful. Each night the dining team will explain where your next dinner is and give you info on dining options for other meals as well. Like they'll tell you which restaurants will be open for breakfast & lunch, etc. So, each night for dinner you will "rotate" to 1 of the 3 restaurants and your serving team will rotate with you. That's why it's called "rotational dining".
Happy sailing!