I was a HCP for the NHS in a former life, but I now work in Education in a term time role. I have one DC with an Autism diagnosis and another who is awaiting assessment. I've worked full time, part time, shifts, TTO and of course there are pros and cons to every working pattern.
I found that when I worked for the NHS, although I was only working 3 days a week at the point I decided to change careers, having gone up to Band 7 the level of stress and responsibility increased dramatically. It just wasn't worth the extra money in the end. I was doing a lot of admin at home in my own time to stay afloat and was too stressed to enjoy my days off anyway. But that's just my experience and I'm sure there are plenty of people working at the same level who find it manageable. Also this was 10 years ago so things may well have changed.
I currently work 30 hours over 4 days TTO and this means that, in addition to no worries about holiday childcare, I get a day to myself every week in term time. For me this is a really good balance. If you decided to stay in your current role, could you make a Flexible Working request to work your hours over 4 days instead of 5? Just a thought.
The holidays can certainly be intense due to the DC's needs. DH takes the kids away for a few days every summer so I get a proper break and that has been a game changer for me. The kids also have playdates with friends, sleepovers and the odd day out with Grandparents which helps. If you don't have those options then I can see why the holidays would be very hard work.
A lot of posters have asked whether your DD would "cope" with holiday childcare. I think this is tricky because there is an element of not knowing until you try, but also kids needs do change over time. My own Autistic DD would certainly appear to cope in a holiday club, but I know she would be masking a great deal of anxiety and this would likely have a knock on impact on her mood, sleep and behaviour at home. Masking at school is exhausting and she needs proper downtime in the holidays, which means being at home with no pressure to conform and fully able to be herself. This need has certainly increased as she's gotten older, whereas other things have gotten easier to manage.
One thing to keep in mind, some PP have said if you take this new job you could always go back to your old Band 5 TTO role if it doesn't work out. Round here the NHS Trust are phasing out TTO roles completely, so all new School Nurses are employed on all year round contracts. I understand this is happening in other areas as well.
Personally, I wouldn't give up my TTO contract for anything. It's what works best for me and for my family. But every family is different and you have to do what's right for you and yours. Best of luck whatever you decide.