Context and knowing your guests matters.
We have family and friends scattered throughout the UK and beyond, so for the vast majority of guests, it was never going to be an afternoon out and drive home in the evening, so we planned it that there was more to do and visit in the area after making the effort to travel. We ended up in a beautiful rural area because the few places in town that could take 100 guests were pretty grim corporate type venues, so for the effort involved anyway, a moderate diversion to the countryside was a small extra. Nearly all our guests can and are happy to drive distances and the few older guests were able to share with close family with little inconvenience.
I knew a few cousins would have to decline as between my work and needs of DH's family we just couldn't get a time mutually compatible to all. Unfortunate, but no offense taken.
Child free could not have worked due to distances. We talked to friends and some were happy and able to arrange babysitters. No one had to decline because babysitting wasn't avaliable.
I always thought it was harsh that a friend was left out of his close family's destination wedding as he was the only one in a small family that couldn't afford to go. Destination weddings started as a way to minimise the guest list, but seem to have grown so that some people expect a full guest list to travel. That is a massive burden of cost and time/ annual leave to place on guests.
I have trekked up to the Scottish Highlands for a wedding on a mountain for hill walking friends. It was just immediate family (very small families) and hill walkers, so worked in that context. It was a wonderful, cosy, low key wedding that suited the couple perfectly. Doing it on a large scale for a different audience would not have worked so well.
Timings such as mid-week, term time/ holidays depends very much on who you know and what they do. Some occupations will need a lot of notice to book leave at peak times. August would be good for education, terrible for the tourist industry.
Just be honest to yourself about what you want, who you want and what the realistic barriers are, and don't take declines personally, especially if you know your plans are unfeasible to your guests.