50 years ago engine manufacturing was rather primitive by today’s standards, and “iron filings” were indeed present in such quantity that oil and filter had to be changed early. Your Honda is the result of an extremely sophisticated manufacturing process which requires virtually no break-in driving past the initial 1000 miles.
However, I would go by what is in the OWNER’S MANUAL, rather than what the dealers says. My Toyota, for instance did not have any special break-in oil and I ran it 5000 miles as per the instruction manual.
As others point out, your car is already broken in, and the trip will be easy on the engine.
Have a great trip!
P.S. Most experts recommend to hold off using synthetic in your type of engine till the 3rd oil change; reason given that regular oil is less slippery and allows the rings to seat properly (wear in) so the engine will not use oil. This makes theoretical sense, and you have nothing to lose by doing it.