I was a TA / helper for over twenty years, in KS1; one class was a combined R/Yr1/Yr2, which might sound unwieldy but it worked well because the teacher was well organised, and it gives flexibility to place children according to their ability.
Yr1 won't be able to organise their time or activities very well, and even things like changing for PE need support. Will you have a TA, or parent helpers maybe?
Once you have a timetable/daily schedule in place, a board with picture representations of subjects/activities/groups established, the children can be taught to control their time from that; children's name labels can be stuck on with Velcro, to show who is where and when!
Some teachers have a similar board for toilet visits, again children can control it themselves once shown. (Yr1 you can still get 'accidents', and some children are shy to ask to 'go'.)
I started as a 'parent helper' supporting reading, and one of my earliest Yr1 girls turned up again seventeen years later, on her final year of Teacher Training! Our roles were reversed, as SHE needed to direct ME in the classroom!
Enjoy it, and come back if we can be of any help.