There was a really interesting thread on here a week or so ago, where people were discussing whether children need to be bored on occasion, and make their own entertainment rather than be constantly stimulated by parents ‘making memories.’
The consensus was mainly that actually, pottering around and leaving kids to just get on with their own stimulation is just fine, and that the pressure to continually be ‘doing’ is mostly self imposed by the parents.
I was born in 1970. Without being too Gen X about it, children my age were generally left to get on with things. There was occasional boredom, for sure, but there were also books, TV, games, seeing friends, hobbies and crafts, walks and just downtime with the family. I was lucky enough to have a warm involved family- just like you do- and my memories of my childhood are fond because I was loved. I don’t feel that I missed out in any way because we weren’t continually going on outings to parks, zoos, cinemas, theatres etc. When they happened it was a treat, not an expectation, or a routine.
Stay home, save the money, put your feet up and let the kids wallow around at home.
Agree with PPs above, do something in late Jan or Feb when it’s still dark and dreary and Christmas seems a long time ago. It’s your holiday too. I hope you have a lovely time.