I used to teach early years/Ks1 in London, and did trips similar to this with children on the tube! If the adults are all teachers/TAs from the school, your DD will be safer, as the staff will know the children very well, be used to shepherding large amounts of infants around busy places, etc.
I've led trips with and without parents. The ones without parents often feel a lot safer- over the years I've dealt with parents wanting to chat to me constantly (so distracting my attention from watching the children), surreptitiously handing out snacks with allergens in when my head was turned, only paying attention to their own child...of course, I've been lucky to have excellent parent helpers as well. But early years teams often have the same adults year after year and function like a well-oiled machine, they'll have done loads of trips like this and may well have done them together, so everyone will know exactly what to do to keep small children safe in a museum/zoo/wherever.
We wouldn't have counted children with 1:1 needs in the ratio. So, say for example, Jim usually has 1:1 TA in class, his 1:1 will attend just for him, and the rest of the kids will have 1:6 supervision, instead of expecting his 1:1 to also look after five other children.
Also, a trip with such young children won't necessarily be what you're imagining. I would never have allowed children off to wander around a museum in groups at this age- we would have all walked around together under my direct supervision, but with each adult keeping a particular eye on "their" six for extra safety. And I'd be head counting relentlessly throughout, every time we changed areas, went to the toilet, finished lunch, etc...I'd also have every kid in high vis so that anyone wandering off was extremely visible.
I'd definitely mention to the teacher that you believe your DD might behave differently outside school, maybe giving some concrete examples so that they understand the circumstances in which she has run in the past. Knowing this information will help the school keep her safe. In my experience, kids see school trips as an extension of school (same adults, similar rules), so behaviour is usually similar on trips to in school. Still, I'd always take anything like this shared by a parent very seriously and put in place a plan to mitigate any risk, just in case.
The teacher will be used to parents being (quite understandably) worried about school trips in reception as for many kids, they're going out and about without their parents with them for the first time. I'd explain that you're worried and ask them to reassure you about what measures they take to keep the children safe. I'd be perfectly happy to talk it through with you to put your mind at ease if your DD was in my class. And it might be helpful for the teacher to update you at the end of the trip- with any luck, it will all go absolutely fine, your DD will have a lovely (and safe) time, and you'll feel a bit more comfortable next time.