You might want to take your bucket directly to a welding shop instead of the tractor dealer. Sometimes dealers just take specialty work to another shop (e.g. welding or hydraulic cylinder work) and then charge you a bit more so they make something for their trouble.
To do it right they'd need to reinforce the bucket with a piece of angle iron or possibly a piece of plate steel. They would weld the reinforcement to the bucket and then weld the hooks to the reinforcement. If you brought the reinforcement steel and the hooks with you, I'm guessing (guessing!) that the welding might cost you $30. If you don't have the reinforcement steel, I think a welding shop could probably supply the reinforcement steel for a lot less than what a tractor dealer would charge (maybe another $10 for a couple of scrap cut-offs).
If you don't already have them, you can find weldable grab hooks by Googling "weldable grab hooks" without the quotation marks, or by going here:
Weldable Grab Hooks at AWDirect
The link to AWDirect was posted previously on TBN, and I ordered hooks from them and was satisfied with the price + shipping and order handling. I wish I could credit the previous poster, but I don't remember who it was.