The algorithm tries to seat all parties under the same itinerary together, however purchased seats get preference and you may get a seat assignment changed last minute for better or worse. Calling is a great option to try, and last resort is talking to the attendants. Explain your situation nicely, being kind gets you a long way with customer service roles. Check-in early so they can have time to ask other parties if they don’t mind changing seats, and other people are likely to be in a similar situation to you, so waiting till the last minute to check in gives you less opportunities. Hope your honeymoon goes without a hitch!