Activities for an older child while working with a younger child?

I have 10yo and 7yo sons. We are in a time of transition with our lesson schedule, and I would appreciate any ideas you have!

I would like to start working with each of them independently in a time block, rather than going back and forth. For example, this is how we have been doing things: I’d work for 15 minutes with the 7yo, and then 25 minutes with the 10yo, and so forth. It has worked okay but feels very choppy at times. After this individual work, we would move on to our morning time block where they are doing their lessons together.

I am not concerned about my 7yo with this potential new arrangement – I am fine with him playing while I am working with his brother. But I guess I am wondering what I could have my 10yo do during the block of time I’d be working with his little brother (about 1 1/4 hours). He is a very new reader, so he is not reading for long periods of time. And because he is a new reader, he is also at the very beginning of writing so I cannot ask him to do much on his own there. I know he would benefit from playing, also, but not for that length of time when we also have a 30 minute break in the morning, and complete everything by 1pm or so. We use RightStart Math which requires my presence, so that is not an option. Some ideas I have had for him: silent reading (15 minutes); math worksheet (he enjoys them!); educational games he can play alone (such as Rush Hour), and whittling. I am wondering how to schedule this, if at all, or to give him the list and let him pick? Do you have any other ideas?

This feels like a big transition to me, but I am sure that is only because it is new and I am so close to the situation. If you have any thoughts or ideas, please let me know!

Thank you so much!