I feel your pain. Really I do. I don't currently have a 2yo. My most recent 2yo turned 3 yesterday!

I will brainstorm a bit here and ramble some too. Sorry if it seems disjointed.
I do know that boys (my boy at least) are very different from girls. I don't know how you have things set up. We pretty much stay in one main area of the house. I allow my 9yo to go to a different room every once in a while to read by herself or work on some independent work, but my others stay with me 90% of the time.
My 3yo is right there with the 5yo and 7yo when they are doing their rhyme time and such. Basically anything that involves movement. When we are doing seatwork or storytime then she is still in the room but must be quiet. Now please understand that quiet is a relative term. My quiet and someone else's quiet may be two very different sound levels.
During all of the this my 10mo is crawling around, nursing, drooling on the books or whatever. But they are all in the same room with me.
At nap time I have my 3yo take her nap in a great big recliner that I can see from where we are working. That way I know if she gets up. My 10mo is still in a crib so it's not an issue.
When you are working one on one with someone have another child do an activity with little brother. Even if it's just a few minutes of singing a song or whatever. Oh! Speaking of songs..... something I have done for years is a family sing-a-long. If we are ever in a chaotic frenzy then I say "time for a sing-a-long!" and everyone sits down and they each get to pick a song to sing together as a family. It's great because it requires very little effort on my part and can be done anywhere. We even sing through the grocery store if needed. Yes people stare, but they would be staring at a screaming 2yo too.
Maybe you could do a little family singing time where you do songs or action rhymes at his level for a few minutes every once in a while. He will feel included and his tank will fill up. That will give you time to work with the others for a bit while he plays.
If he absolutely wants to be involved, then I say
involve him! Grab a piece of scrap paper and let him have a glue stick. If he still uses a high chair then strap him in and let him at it! If he's not strapped then just give him washable glue and crayons. I'm all about prevention. If they are cutting something then give him some kiddie scissors and some old magazines and he can cut cut cut. I pretty much let all of them be involved if they want as long as they are not a disruption to the one that the lesson is actually for.
hth!