This is so not a big deal. If you honestly do not think this is something he can handle or is something you do not feel is important, don't make him do it.
I always say, homework is for the child, not the parent. I did not hover over or around our child. She knew if she needed help to just ask and I would gladly assist with answers to her question. Sometimes, she just wanted me close by.
In schools, they no longer teach "Typing". That is so far gone. It is now keyboarding and most families with computers allow their children work with the keyboard to help with spelling, fine motor skills etc. It is just one more thing we can use as a tool to reinforce learning letters.
This teacher is doing enrichment. I always loved this with our daughter, because it gave me ideas on fun things to do to help our daughter expand her learning and learn new skills.
I am guessing it never occurred to you to let your child play on a keyboard? Nothing wrong with that.
If he becomes frustrated, just tell him," it is ok, this is your first time, just do as much as you can and then stop, Teacher just wanted you to give it a try."
Have him do HIS best on this assignment, No apologies needed if it is not perfect OR even not completed. If he did his best, Awesome! Just write a note, "first time on the keyboard!" lets her know this was a new thing for him.
Our daughter has always been very bright. There are things that came easily to her and other things she had to work really hard at. BUT I never did the work for her, I never made her finish work that was too difficult, I would ask her. "Did you try? Did you do your best? If she answered yes, I left it at that.
Not to brag but just to give you an idea, she was towards the top top of her class Not quite top 10% but was a National Merit scholar in the end. But she did not get all A's, instead she got the real grades that SHE earned. Not me sitting there correcting everything, or making her redo her work unless she felt she wanted to or needed to.
He is only in first grade, he has many years to learn to be proficient on a keyboard. This summer this can be a fun thing for him to practice. I recall in 4th grade is when they started turning in real reports that needed to be sent printed or emailed to the teachers. Good thing because once they were in 6th grade, that was 90% of how the reports were sent in.
Just relax and reassure your son, if he did his best, that is awesome!