I have two lefty sons of two righty parents, talk about confusing.
DS10 has been predominantly left his whole life, in fact teachers commented on how left he was at such a young age. He writes left and throws left but bats right and golfs right. His handwriting is actually really nice, a retired nun at his school helped him

. He had the hardest time learning to tie his shoes. I bought him abook and that helped but he still doesnt tie them tight enough. He is FOREVER getting pen, marker and pencil marks all over him and his clothing (if anyone has a suggestion for getting those stains out of cuffs of school uniforms would love to hear it, yes I have tried bleach). Anyway the thing that cracks me up is that you all keep saying these lefties are creative,
DS10 does not have a creative bone in his body, he is facts man! His art work struggles big time, his cutting looks awful and when he draws something freehand I have to ask what it is, that is not good in 4th grade.
Now DS4 has a condition called hypotnia or low muscle tone in his trunk and this has affected both gross and fine motor skills so for the longest time he would not pick a hand, it was hard on the OT that works with him to work on things when his brain couldnt decide. Well over the summer it seems he has become a lefty too and now that we have a hand dominance he is progressing in so many areas.
Good luck.