Feeling awkward/mean excluding a friend

[Livelifelaughter]

I have a group of friends that I holiday with. One in the group isn't particularly fit, she won't do much that is active and the rest of us like to hire bikes, go on a hike etc, go for a run, swim in a lake. Usually this isn't a problem as we will go on a City break. However, we have been doing more active trips which we invite her to...the trouble is we seem to go through a charade of her saying how excited she is to go and then backing out. In the last couple of years it's happened a lot. She will never say it's because she doesn't like the activity. An example is that a few of us went hiking in Iceland, she made an excuse not to come saying she would have loved to go hiking there. It's really annoying, there's a list of things she would "definitely do" but has turned down, such as Hiking Mont Blanc, Skiing. Because she doesn't say that it's not her thing or similar we go through looking at hotels to include her, working around dates to include her and then she will say she can't go, not that she has changed her mind but that she can't go often with no reason or a fairly lump one.
Anyway, now we are arranging trips without her and I feel quite mean about doing so. I don't really know how to deal with it.. Any suggestions...

This is perfect - do this. This will cut out the pretend "yes I'd love to go" and then backing out. Tell her that you have to pay upfront and refunds might not be possible.

OR, just talk to her. Say "hey X, I'd love you to come with us but you often cancel at the last minute which is difficult for us so please feel free to be honest if its something you arent interested in- we won't be offended and maybe we can arrange something else next time that you like"- that is perfectly polite and reasonable and if she gets in a huff about it then I'd distance myself from her. It's rude to ask to be included in plans then constantly cancel when people have specifically booked annual leave to accommodate you.

@rookiemere I am a terrible at skiing but love to go, so will have lessons and see friends on the mountain but look after myself.

You"D think reading this that my friend is a half wit. She's not, she's great company but her Achilles heel is not fessing up to what she can and can't do. Outside of holidays we spend time together. The holiday thing is once or twice a year, most have families and limited annual leave, and anyone in the group can arrange it, it's not always done by the same person. That being said all bar my friend really prioritise fitness because at our age it seems more important to keep fit and active and enjoy life. When we were younger we were far happier sitting in cafes all day or shopping on trips. A couple of the group have been seriously ill and really made an effort to keep fit and in shape and actually wanted to do things that might be precluded by age later on.

In your 50s you can't take your body and health for granted so you want to achieve things, like complete a long hike or swim in a lake.