I work in a school (admin, not teaching). Every year for the last 11 years, I've been away on my own over the summer half-term to attend a big literary festival. My DH and DC have never wanted to come. Both children are now in their 20s.
I register as a volunteer for the festival, book a campsite for a week, do my volunteering duties and attend events at the festival, read, sleep lots, eat what I want and do some work remotely. I have several friends who do similar. It's my 'me' week and I look forward to it very much. Several people at work know what I do and occasionally they turn up at the festival for a day or two. We bump into each other at the festival site, have a coffee — not a problem.
Last year I arrived on the campsite and was setting the van up when someone banged on the window. It was a colleague with her 7-year-old daughter, asking for help to put their tent up. They were camping on the same site in a tent for the week. I helped out, reluctantly. Then they wanted to come in and join me in the van because there was a chilly wind and they were cold. I made them drinks, they poked around the van and didn't seem to want to leave. It went on like that. The weather wasn't great and whenever I was in the van they'd come round and expect to sit with me in the warm or have hot drinks or a meal. They had a car and went out sometimes during the day, but never brought back a takeaway or food to help out. I felt under pressure to host them and so ended up avoiding the van as much as possible. One evening my colleague asked me to look after her daughter while she attended a comedy gig at the festival. She'd already bought a ticket: I didn't feel as if I could say no. I felt as if I'd lost all my down time to looking after them.
They left a day early, which was a relief: they weren't prepared for the reality of camping and from what my colleague said in the weeks afterwards, she had no intention of going back again. Yesterday afternoon I bumped into her in the corridor and she announced that she'd bought a better tent and mattress and thermal leggings and she and her daughter were booked again. Same campsite as me. 'We can hang out like last year' she said.
I'm already booked into the campsite and on the volunteer rota, so I'm committed. How can I politely say that they spoiled last year's break for me, and I'm not doing it again?