Hi
I was an Infant School TA for ten years, and introduced children to informal (ie not often using printed music, and not aiming for Grades) music learning on recorder, percussion and keyboard. My Yr2 recorder groups gave little performances for parents, and some children carried on into the Junior School. One year when they had moved up to Yr6 they asked me to arrange for them to perform for the whole school, before they transferred to Secondary, which I was happy to do of course. With Yr2 I coached children on percussion for the Christmas production.
So yes, playing any instrument is enjoyable and a valuable skill. Some things to consider: the child's build and size of hands; ability to concentrate, and 'stick at' an activity; type of music they already know and enjoy.
My DS played recorder from age 5, then trombone at 7 or 8, though he really want saxophone, which he changed to aged 10.
Violin, cello etc are more difficult to learn. Trumpet needs a lot of 'puff, and trombone, though larger, is easier to play. Recorder is a good introduction to go on to flute, clarinet, and saxophone.
Do you and/or DS prefer Classical, brass band, lighter orchestral, jazz, etc ?
So there are many options available.
Good luck in you choice!