If you have some extra cash to spend you may get offered a buy up to business that would be worth it, but may equal the cost of your ticket. Reserve your seat in advance if you can and check seatguru to pick a good one. If you cannot reserve checkin online 24 hours in advance to get the best seats.

Definitely tell the Flight attendant you are on your honeymoon (not in an asking way, but as sharing your excitement) they may give you something small like a glass of champagne, but don't expect it.

You've got some relatively tight connection times so make sure you know exactly where you're going and walk quickly. The Harrisburg flights operate at an area of the airport that requires a long walk. As you're going to an international flight luckily you don't have to clear customs and have a short immigration check with small lines. Don't go downstairs to the main customs hall follow signs to the international connections if you are confused ask someone for help. Air Canada's website has good information on this.

There is a risk that you make it but your bag is delayed so if you need to check luggage, make sure you have enough in carryon to last a few days. Finally if something goes wrong with your flights make sure you push the agent to put you on any available routing not just the next air Canada direct flight that could delay you to the next day.

Although almost two hours in FRA seems like a long time it will require you to walk quickly. The connects to the last AC flight of the day but you may want to research other later Lufthansa or United flight back through the NE US to get you home if your first flight is delayed. If you do arrive too late for your connection talk to the Lufthansa gate agent about other flight options and let them know if you are flexible with other destinations than Harrisburg.

Having said all that congratulations and don't worry too much about delays or challenges. Most flights are on time so don't stress out, but do be prepared and ready for the worst case. For jet lag try to sleep the entire flight to Rome; bring eyeshades and ear plugs if you can and then force your self to stay up to 9/10pm that first night. You may be tired that first day, but will force you onto the new schedule and prevent having challenges sleeping that first night if you sleep that afternoon.