I actually sympathise with you Ginandtea.
Hopefully, 'weddings are a once in a lifetime' and whilst we endeavour to accommodate our nearest and dearest as well as trying to ensure 'our' day is about 'us' and incorporates all 'our' dreams and wishes, there will be SOMEONE who won't be happy with your decision, unfortunately.
Even compromises have to be made with our 'dream-come-true-wedding'.
I had to make sacrifices. I wanted a 'large' wedding of about 80 guests - church wedding, wedding breakfast and evening entertainment with photo booth, casino, soft play for the kids and a disco/band. It wasn't to be! DH is an introvert and wouldn't have liked being centre of attention of so many people.
So my wedding was still in a lovely mansion type hotel, but with just 32 guests, civil ceremony, wedding breakfast and then quiet evening in the drawing room with a small buffet (which nobody ate because it was mainly older people who were just about dead on their feet at 8pm!) and we had only 2 children - groom's toddler and friend's six month old baby who was breastfed (we said no children because there was nothing for them and they would be utterly bored).
I had one person who couldn't even be bothered to respond to my wedding invite - a friend whom I was bridesmaid for 8 years previous (although her mother tried her best to remove such a role from me because she was worried I couldn't walk down the aisle after a car accident - the bride's car! It was utter tosh and actually looked down her nose at me - they're 'upper class' let's just say!) The reason (I think) she didn't respond and thus never spoke to me again was because I said 'no children'.I had other guests who understood and abided by the rule but she was 'apparently' pissed off. if she was having trouble with childcare, I would have allowed her children to attend (ages 7 and 2) because it wasn't my dislike of children (am a teacher) it was because I didn't want to put undue pressure on the parents and allow them to relax and have a good time!
IF this is truly your dream wedding venue and you don't think you would be happier anywhere else (I understand - I married in my 'home' county a good 150 miles from home and most people had to travel with us) then I think you should go for it. You said 75% wouldn't have an issue. If some guests regretfully decline and cite accommodation costs, you could always then offer to pay for their rooms. At the end of the day, it is up to the guests to accept or decline but anyone declining and then give you the snub because of where YOU want to get married, then they're not really friends are they? I had to explain to a lot of my friends why i couldn't invite them to the wedding (cost was because of it as well as DH being an introvert) and apart from that one friend with children, the rest understood and wished me well anyways!
if this was me, I would book my wedding at Gleneagles (despite their stupid rule), pay half for everyone's room if that is what you can afford. You might be pleasantly surprised!
But you also sound lovely for thinking of your guests when it is YOURS and YOUR FIANCE'S day!