Primary schools have two formats, either the short timetable - orario corto - and will finish at 1pm but with school on Saturday morning or long timetable - orario lungo - and will finish around 4pm with no school on Saturday. Families are able to pick which system they like and want. Orario corto will have some homework during the week, usually a consolidation of what was done in class, so if they learned long division that day, they will have 5 more to do at home, or some questions in their science, history or whatever textbook. Children who attend the long timetable have no homework during the week, only at weekend.
School system is very different from UK, but that is expected. Italy is very different from UK on every front, from food to health care. and everything in-between . Your kids will have a paediatrician and not a GP as an example.
Yes, there are plenty of memory tasks, from learning a small poem every week or fortnight , to timetables. This however is an advantage, because memory is a muscle in many ways, if you exercise it early on, it will be an advantage in later years. Same with writing. To be able to write longer text, you need practice because fingers hurt after a few lines. Copying a paragraph is both useful for dexterity and handwriting.... and so on. There is a reason behind every activity.
Definitely different, how could it not be? Is that a bad thing? Isn't it the point?
The teacher will not expect the child to do the same levels of homework straight away. They are used to other nationalities joining in, and the system works.
Give it a go, your DC8 will help their classmates with English, they will help them with Italian. Organise playdate or a "merenda" afternoon snack at your house, make it fun, offering marmite to whoever wants to try it and test it against Nutella . Kids are curious and welcoming. Of course, it won't be easy peasy and that's ok. A little bit of struggle/adversity is actually a good thing to experience when accompanied by the love and understanding of a parent.
Learning some Italian beforehand will not help much, because the speed at which people talk in real life is very different, so they won't understand a single word despite studying and it might actually backfire because they could feel more lost having put effort for nothing.
Instead , use Italian words in the house, for common stuff, so acqua when offering/asking for water. Scarpe when putting shoes at the front door. In a fun way and make mistakes that they will correct. Turn Italian into a post-it game, putting labels on stuff and have them quiz you and you will exaggerate and talk with your hands with a loud voice .
That learning, yes. A formal tutor, a course, or even duolingo. Tedious with zero benefit.
In the end, it will be your attitude and input that will give the stay a certain tone. Take it as a joyful gelato-filled adventure.