Arriving at Athens Airport an evening prior to our Visa start date

So we're a married Indian couple on our honeymoon trip to Greece. Our original flight from Mumbai to Athens (via Muscat) on Oman Air was scheduled for July 10, 2019 and arriving at Athens at 1950 hours on 10 July. Basis this schedule, we had applied for our tourist Visa with the intended date of arrival in the Schengen area as 10 July.

Today I received a call from the airline informing me that our onward flight has been cancelled due to B-737 Max grounding. They can accommodate us either on the 11 July flight (in which case we miss the first day in Athens) or 9 July (in which case we arrive at Athens at 1950 hours on 9 July itself).

If we decide to take the latter route, i.e. reach 4 hours prior to the midnight of our intended date of arrival in the Schengen area - How likely are we to face difficulties either in (a) Mumbai (i.e. origination point) or (b) Muscat (where we need to change aircrafts) or (c) Athens itself with the security/ immigration authorities?

We will, of course, wait until midnight of 10 July to pass through immigration. But I'm concerned if we will face challenges explaining our situation or with our checked-in luggage or with the transit authorities in Oman itself.

If anyone knows of a similar situation or familiar with Greek immigration, would love to hear you out. The safer (albeit, inefficient) option is to just cut our trip short by a day and reschedule to 11 July.

Thanks!