I am going to state my own opinion here, please understand that this is not an attack in any way. I'm simply stating my beliefs and some facts on these birds.
Greys pick up all sorts of sounds in their environment and you are never going to find a grey that doesn't make inappropriate noises. No matter if they're a rescue passed through drug deals or the angel baby that you hand raise yourself. No matter how controlled the environment, someone will make a noise you do not like and a grey will pick up on that in no time. Especially is this bird is to be exposed to many different people every day. I do not believe any greys to be therapy birds and a vast majority are extremely hands-off birds. They are very high-strung animals that need to have a very stable environment. They do not like to cuddle, they don't like to sit around doing nothing, and they are not going to be quiet when you want them to be.
You said you had a grey previously, and I am very sorry for your loss of him/her. It sounds like he/she was a wonderful companion to be around. I understand that you want to get a bird that would be good around children and would be good around people who need therapy animals. Children are unpredictable and people who don't know about parrots aren't going to be able to learn how to handle them after a short introduction to the bird. It takes months if not years of learning from correct and informed resources to be able to know how to read parrots and respect what they portray through their body language. The bird will act out if anyone does anything that the parrot finds upsetting, and this can result in a nasty bite.
Also, please do not get a bird with a million expectations for them. If you have high expectations when it comes to parrots, you'll only be let down. No bird is perfect, hand raised or passed through many homes, and everyone interested in bird has to be sure they understand this before getting one. If you want to keep your expectations, which would be a must if you're to have this bird around and handled by non-bird-people, you'll need to spend so much time training. If you are busy and have less than several hours a day to work with them and reinforce the behaviors you want, this won't work. If you don't keep up with training and constantly reinforce these "good" behaviors, then the "bad" will begin to come back. Birds need time and if you don't have the time for a bird that is going to need to have very specific and important training, it's not going to work.
Long story short, there is no grey (or parrot, for that matter) out there that will be perfect. There's no bird that is going to never make any obtrusive sounds, never bite anyone who they "decide" isn't good, and always want to be touched and cuddled and moved around all the time. It takes time and training to get a bird to do certain things and even after training there will still be many "bad" behaviors that are just bird behaviors. Many things in parrots cannot be untrained.
And what happens if the bird you hand raise and train for years turns out to hate other people and isn't comfortable with them? If they learn an awful sound that you cannot un-train? Will you continue to love that bird unconditionally or will he/she end up in a rescue for the nest decade waiting for someone to come along? If you get a bird just for one purpose and they do not fulfill that designated purpose, what will become of them?
If you want to train a therapy animal, I would highly suggest either going for a smaller bird that can't do as much damage or just avoiding parrots altogether. They are very amazing animals but I personally don't believe any species, hang raised or rescued, are fit to be therapy animals. I truly don't mean to sound harsh in any of this, but this is the basic truth that I see to this situation. And I can only imagine it ending badly.
YES!!
