I tried to answer earlier. My puter is being ornery today.
I have four kids. Oldest plays the trumpet, next one the violin
My younger two play the piano, My third has taken drum lessons, violin lessons and she just started the flute. She is 13.
My 4th plays the piano and has taken trumpet lessons and just started the clarinet.
Suzuki Method teaching does not teach the key signatures or how to read music at the very beginning. It teaches them to play by watching the teacher and copying. I am not a fan of that.
My violinist was taught Suzuki method.
She wished that I had started her out on the piano. She can't read the bass clef.
My son plays the trumpet, he also says he would have liked to learn to play the piano, if for no other reason than to know how to really read music. He still has trouble wiht his guitar books, he is teaching himself guitar.
My little ones started late, at 11 and 9. In other countries to really be the piano or violin virtuosos they start the children at 3 and 4. Do you really think your child will want to play at Carnegie Hall? I dont' think mine are headed there, they want to learn becasue we have a huge grand piano in the house and they are not allowed to play it unless they are playing a song.
I would start him on the piano, private lessons. Get him the cello after he can read music or has a grasp of it.
I had 8 years of piano lessons as a child. Because of that the only musical instruments I cannot play are the brass. I can pick up any instrument and once I know where one note is I can figure it out, woodwinds, strings, flutes, recorders, etc. He'll get there too. Plus knowing how to play the piano is just a great skill. Every church has them, most schools, even some hotels.