What are the best shoes suitable for wearing to a formal race-day or polo day (horse racing)?

Long days (often involving lots of champagne) on grass lawns require careful footwear choices.
Things to consider are:

Comfort - 5+ hours standing in heels requires a comfy shoe so cushioned soles get a big tick!

Stability/heel size - nobody wants their heels to be sinking into the grass/teetering around on uneven surfaces on pin-thin stilettos so think block heels or wedges

Formality - these are formal to semi-formal events so a shoe that's great for a long day at work but not so pretty or a party shoe that's studded and edgy may be comfy and stable but not suit the theme off the day

And here begins my dilemma! So many considerations!