My wedding was the only time I was able to have almost everyone I loved together in one place at one time and it was amazing for that. I'm an army brat by background so my relatives and close friends had mostly never met as they were hundreds of miles apart. The DJ played a good mix of modern (at the time - 90's) and floor fillers that all generations liked. One of my favourite memories is seeing my grans up dancing with my friends to Whigfield Saturday night and blue girls and boys .
I've also worked in the wedding industry and the things guests most appreciate are:
Not being kept hanging about
Decent food with good choices (as a veggie please do a decent veggie option) - we did a buffet which was fairly non traditional but our mix of guests meant it was a lot easier than a sit down - veggies, allergies, religious factors would have made it really hard to find even one dish that suited everyone! And don't make guests wait forever to be fed! Especially if some have had to come some distance to attend, make sure SOMETHING is available pretty much on arrival at reception.
Good non offensive non niche music (the couple may be trad jazz fans but it's unlikely all the guests will be!)
Plentiful and comfy seating
Reception room temp optimal (too hot is not good but too cold is even worse that really pisses people off!)
Good, clean, well maintained bathroom facilities (some venues can be really poor on this and overlook it)
Personally I'm not a fan of child free weddings. I was raised they are a family occasion and that means everyone. I find it very odd the idea of excluding children from a family event. Also I love kids of all ages, there were loads of kids at my wedding from newborn to teens and they all behaved pretty well and were enjoyed by the other guests. The older ones happily played with/watched the little ones when earlier in the day they were playing out on a grassed area outside the reception hall (it was a "village hall" type place) and also helped older guests by fetching drinks etc and they "taught" us all the latest dance moves which was great fun. The more outgoing/avuncular guests loved having an audience for dad jokes and cheesy magic tricks
At one point a friends teen was teaching grans the moves to Saturday night while my auntie enjoyed lovely new baby cuddles with another friends newborn
Everyone said they loved the buffet as they didn't have to worry their dietary needs wouldn't be met and even the "coolest" music people fully embraced the cheesy floor fillers and were up dancing.
@cissyandbessy I'm with you on the overly formal nonsense. A friend of mine (lovely person, not so keen on her husband) had a massive formal and expensive wedding the year after mine, many of the same guests on the friends side. It was beautiful but it was SO formal that many of us felt out of water and couldn't relax, when the music (small band playing quite formal and even classical pieces at points) started in the evening and nobody got up to dance bride got quite stressed, but nobody felt brave enough to be the first up and maybe do it "wrong", there were 7 sets of cutlery ffs! Sit down meal and as a veggie I was frankly made to feel I was being "awkward" omni guests had only 2 options a rich beef dish or fish and several commented they liked neither. Only one dessert option.
Yet I knew they had spent an absolute fortune.
Just shows it's not about how much you spend, you need to tailor it to suit the attendees. This was a beer and chicken crowd and they tried to make them something they weren't.
The divorce 
well yea I'm divorced now - but the wedding was ace!
Make sure a buffet has plenty of veggie options, as meat eaters will still eat those too.
Oh definitely! Our wedding was a catered buffet, the mess did it for us (dad called in a favour!) so I guess more like a carvery type set up? But with plenty of veggie options
Otherwise, the best weddings I've been to have had plenty of food and drink (including tea and coffee, not everyone wants alcohol)
Yes! My mum said to make sure tea and coffee was available and I was a bit 
when she made the suggestion - on the day I reached a point myself where I was gasping for a basic cuppa! So glad I took her advice on that and I "paid it forward" when I went into the industry myself
all generations of family (as per Peter Kaye) with DC running round and great aunts having one sherry too many. Lots of warmth and love
Exactly!
Even as an independent observer later in life I noticed how much more relaxed, friendly and fun weddings WITH children are.