The magic number in bilingual research is 20% of a child's waking hours spent interacting in a language in order for the kids to be fluent. So a few hours with a tutor each week would be great enrichment but it will take a lot longer for the time to result in fluency.
I can't remember if you said you were planning to do French immersion kindergarten, but if you are then having your child have that time with a tutor or in a fun language class would ease that transition and let him hit the ground running.
My kids go to a dual language immersion school and the kids who had some exposure to the target language either by way of a class or a tutor or a parent or grandparent who sometimes spoke to them had an easier time in the beginning than the kids who had no exposure.
It sounds like you are trying to also set the accent with the tutor. Kids can be pretty adaptable in their accents. I have seen kids who speak in a very different accent to their parents than they do with their friends in order to communicate with their friends more easily or to fit in.
There are many bilingual parenting boards out there and there are some great books too - The Bilingual Edge is probably my favorite. I believe that has at least a chapter on raising kids NOT using the immersion methods of OPOL (one parent, one language) or Home vs Community but having children spend time with a tutor or take a class.
I totally agree with Max's mom that the relationship with the person speaking the languages to them is going to have a huge effect on how well it goes. Having a parent or parents or primary caretakers will be better than an occasional tutor, but having a fun tutor who is amazing will be much better than having someone who the child doesn't "click" with.
I think you are on the right track to make the language exposure something so much fun that it is irresistible! Your energy and attitude would have a profound effect.
There are many parenting forums specifically related to raising bilingual children out there so you can find even ideas and support on adding French to your child's life.
Good luck!
