Although morally, all 'non essential' absences rom school are equally, in reality it depends a lot on what th school will be doing.
I do know of some schools where SATs are given such high importance that, frankly, once they are over almost no learning happens - the Y6 teachers see it as their role to cram for SATs, and after that it is basically free time punctuated with some enjoyable activities.
In other schools, SATs week is simply a short interruption to the real business of teaching and learning, and the pace of learning in Y6 is maintained pretty much to the end of term (as it is for all other years) to set children on the right trajectory for the start of Y7.
In yet other schools, a different type of learning takes place - residential week, preparation for a school play, cycle proficiency, life skills such as first aid, ciooking, budgeting, and work skills such as IT, presentation, debating etc take centre stage. If this week meant that your child was e.g. the only one without a part in the Y6 playm, would that create a problem?
I would, in your place, have a discussion with the Y6 teachers, and guage their response. i would also ascertain the fining cstructure in your area. Some areas interpret the £60 per session very literally - so at maximum that could be £120 per parent per day, as each day has 2 school sessions. 5 days in that scenario could be £1200. Others do £60 per 'period of absence', so £120 for 5 days for 2 parents. This is NOT under the school's control in any way.