If Fredo had not been killed, what do you think Anthony would have grown to be? It seems from GFIII that he didnt want to get mixed up in Michael's business because Fredo was killed by Michael. But, assuming that Fredo wasnt killed by Anthony's father, do you think maybe Anthony would have partaken in the family business?
I think there really isnt a clue as to what he might do in such a case. However, maybe Kay would have forbade him from it....

Kay was already trying to shield Anthony from his father's 'business' ... long before Fredo was killed.

Chances are that even had Fredo lived and gotten away with the trecherous, selfish betrayal against Michael and the entire Corleone Family...between his mother's influence and the seemingly tender relationship that was beginning to develop with his uncle, Anthony might still have rebelled against the violent nature of the family business.

But that's not to say that Michael would've even wanted Anthony to follow him into the Family, despite that 'Maybe I can help' conversation after the Communion Party. He may have had those 'Senator/Governor' plans in mind that Vito had once had for him.

After all...when you're 3 years old and can read the funny papers, there's just no telling how far you can go!!

Apple

I had always taken Kaye's comments to imply Anthony had some sort of emotional or developmental problems - until GFIII of course, then I just figured he had a terrible agent.

In my pre-GFIII I picked Anthony growing up to be a useless stay around the house sort of guy that would be constant sorce of frustration for Michael as he realized his son was not at all what he wanted, but for once in his life could do nothing about it. Some problems money and violence can't solve.

I took the bonding with Fredo to reinforce this notion, birds of a feather.

I think the short answer is that Fredo's survival probably wouldn't have had much, if any, influence on Anthony's career direction. Yes, he said, "Maybe I can help you?" but he was too young to understand the true nature of his father's business. And, as Apple points out, Kay was already pulling him (or poised to pull him) away from "the family business."
In Kay's confrontation with Michael in III, Michael wanted Anthony to go to law school and told Kay, "He throws away greatness." I don't think he meant that Anthony would be a great champion of law, which supports Apple's contention that Michael probably intended him to be a Senator or Governor, as his own father wanted for him. The knowledge that his father ordered Fredo's death might have had an impact on Anthony's break with his father, but I think he'd have chosen out without knowing about Fredo.
Apple: I didn't take his achievement of reading the funny papers at age 3 to indicate a future as an illustrator or cartoonist. I thought that his prowess with the flit gun portended a future as an exterminator, particularly since Vito keeled over shortly thereafter. This was an old family tradition, as in Clemenza telling Paulie: "Watch out we don't extoiminate you."

Of course, the fact that he cried like a little weenie at grandpa's orange monster teeth...may have also been an early indication of the sensitive, artistic side of Anthony which would of course come into full bloom by the time of GFIII...

If that were the case, he'd have made his debut in "Pagliacci" instead of "Cavalleria Rusticana."

Actually these two rather short operas are shown together.

There are deleted scenes or script drafts that show Anthony was an emotional wreck well before Fredo died. There is a scene at the communion where is is sitting alone all morose, and also in New Hampshire where Tom goes to retrieve Kay when she leaves Nevada. ALso in GF II there is the "abortion" scene in which Kay says something about Anthony's not being "all right."

No she was saying that his life isn't right. He has no friends his age. Just Michael's Buttonmen to play with.
See:
KAY:You've become blind, MICHAEL.
MICHAEL: Blind to what?
KAY: Look -- look what's happened to us, Mike -- my God, look what's happened to our son, MICHAEL.
MICHAEL: Nothing's happened to him.
KAY: Don't tell me nothing's --
MICHAEL: ANTHONY's fine
KAY: ANTHONY's not fine!
MICHAEL: I don't wanna hear about it.
KAY: You will hear about it!
MICHAEL: I don't wanna hear about it!
KAY: ANTHONY's friends --
MICHAEL: I don't wanna hear about it!
KAY: are your buttonmen!
MICHAEL: I don't wanna hear about it!

Actually, I think DT is referring to the scene in a draft script here where Tom tracks down Kay in New Hampshire.

Kay elaborates on what's wrong with Anthony, telling Tom, among other things, that Anthony knows Michael killed Carlo and that Anthony is afraid Michael will have him shot to get revenge for his "killing" Vito.

See--I told you that flit gun in GF was more than a prop...