Walk from ceremony to reception

I wanted the ceremony part outside-if weather permits of course
There is a little park beside our venue I rented a pavillion months ago
Fmil never liked my idea because I didnt get the pavillion that is closest to my venue
The walk is completely flat and really is not far. Maybe about the distance you would park at the walmart and walk to go inside the doors
Fmil is saying now that fhs grandparents might not be able to make the walk to the ceremony and back we should have it insidr the venue
I really wanted it outsidr have already paid for my pavillion and fmil wss there when I did pay and never came up with this reaso. Til now...
Who has had ceremonies that were a bit of a walk? I know ive read some on here and they sounded like a pretty walk in the park to a ceremony
How does this go with guests assuming a wedding is casual? Not expecting ppl to wear heels and tuxes type thing