Everyone knows that I'm not a fan of Yamaha arrangers for myself, but, in this case, the 900 would not be a bad choice. Lots of available styles and help from users here and other places.
Price is good, and the final product is good enough for lots of people to work and get paid.
It seems to me that it would be a good first arranger, since the learning curve is shorter than on some of the other brands, and still be good enough so you won't quickly grow out of it.
And, slightly off topic, but my grandson is my part-time drummer, and my son is my bass player. It really can't get much better than that. Music is a great thing to do with family.
I'd GO FOR IT!
R.