Cowens, you won't know your actual seating time until you board the ship. The dining room and time will be embossed on your Sail & Sign card. If you want to change it or request a table size, go see the Maitre 'd.
When you get to your cabin, there will be a copy of the Capers, the daily newsletter, in your cabin. In there will be an announcement as to what time and where to see the Maitre 'd. If possible, he will change your table and/or dining time.
About going to the cabin when you board - I always board fairly early, around noon, and I go directly to my cabin. On every cruise so far, it's been ready. I drop my carry-on luggage, and head to the Lido Deck for lunch. My other luggage is usually (not always) at the cabin door when I return to the cabin.
Muster Drill is held just after sailing, on most ships. If your ship sails at 4pm, the drill will probably be around 4:30.
And - don't ever apologize for asking questions.
That's what these boards are for. I've been on 12 cruises (9 on Carnival), and I still learn things from the boards. Hope y'all have a fabulous cruise! Bon Voyage!