OP, you sound very much like someone I know, not a peer but a younger woman I work with. She too lives out of the way in a small cottage and is probably the last of her peer group to be without children. She often complains about lack of effort from her friends while suggesting that she does understand how things are when you have children...
As an outsider I can see that her expectations are off and she (like everyone who hasn't actually had children explode their lives) really doesn't understand how life changes when you have kids.
She cant really see that when kids are really young, often weekends are more exhausting than weekdays...especially if you are trying to keep your kids safe/under control/fed&watered in someone else's house, or a pub/cafe/restaurant you aren't familiar with (there's good reason people stick with favourites at this life stage)...
She doesn't seem to realise that a massive portion of her friends income is now committed to childcare, so known places with cheap deals and food that will definitely be eaten are preferable...
She doesn't realise that inviting friends with children to travel any longish distance to visit will completely mess up napping routines (young kids often fall asleep on train/car journeys whether it is their usual time to or not) and leave the parents with a sleepless night later...
She doesn't understand that some small children have very early waking times and after the working week both parents take turns for a lie in at weekends to cope with this stage...meaning no one is really going to enjoy an early start to set off in a long journey in time for lunch.
Essentially she doesn't understand that her friends lives are now driven by these tiny bosses and that if she wants to maintain these friendships she needs to take her lead from what they feel they can manage. At least until children are a little older and it's more common for each parent to take a break...largely because the DCs growing independence means this break isn't too burdonsome for the parent left behind.
Instead, she invites them round, enjoying setting the table for dinner and preparing things in a adult way not really understanding a lot of these niceties are lost when you are just doing what is safe, necessary and practical around children. She does try to accommodate the children without really taking a lead from the parents and misses the mark.
I wonder if your friends anticipated that the get together wasn't really going to work for them and as soon as you started to indicate that too, they simply took this as a get out clause to allow them to suggest something more practical.
None of this is personal, don't make it this way, and hopefully you'll still have these friendships as life moves on. The younger woman I know takes this very personally and feels let down...when really it's all just a question of practicality. Her angst is unnecessary.