I understand why you're upset-i would be. I wouldn't leave it with them,again, either. It's a really big thing , leaving an animal that you love, that's dependent on you, (or whoever's caring for it) , for it's well being- and if you leave instructions for it's care they should be carried out, as well as possible.
If I'd left a dog with a relative and said don't walk it- just let it go in the garden , I'd be really upset , if I found they had. Can you contact them , as soon as possible and say, your daughter's upset and you're worried, can they give you their word to just let it go in the garden, (and keep an eye on it while it's there), because it's spoiling your holiday, having to worry.
If you don't feel you can trust them, and if you or your daughter are at all worried- I'd consider cutting your holiday short and going home early, if it's at all possible, even if it meant some extra expense. If you can't , I would tell them as firmly as you can , that you don't want it being taken out on walks by them, say you hope you can trust them- but if for any reason they do take it somewhere it needs to stay on it's lead , because it's recall's not good. Years ago, when I was a child, we lost a lovely dog , that didn't come back well, and got run over- it was very upsetting.
Another time, I'd try and find good reputable kennels-try and look around for a nice one, I do sympathize about finding suitable kennels, it can be difficult- but some are good ones , years ago we use to take our rabbit to a kennels, that took other pets and they had a nice safe field that they walked the dogs round. If you find a nice kennels, one thing you could try is letting your dog stay for a night or two, when you're not away- to let it practice, and then if there is a problem you could go and fetch it.
When you come back, maybe you could start doing some recall training. My grown up daughter has dogs , I sometimes help her with recall training- we stand facing each other, fairly close, on a safe enclosed space, and the dog sits by my daughter , then I call it really enthusiastically to me and she tells it to go to me, and when it gets to me I give it a treat , like a bit of sausage or dog biscuit, and really praise it, then as soon as it's eaten it -my daughter calls it back to her, and so on. We do it back and forth 5 or 6 times. My dds dogs did improve their recall doing things like that- (though one is getting a bit old now, and gets a bit nervous, and has bolted a few times so it's on it's lead nearly all the time, now)
Anyway , good luck and I hope everything's ok- and you aren't being at all unreasonable- it would upset me a lot.