To escape my little ones I moved out into a whole new
building!
(My husband was having a new garage built and I took over half of it as my own.) OK...probably not the answer you're looking for but it does work -- especially since there is a lock on the door! But when I have 4-year-old Morgan at home she does sometimes hang out in the studio with me. And the best thing to keep her out of my toys is to let her have some of her own. Morgan plays with my Russian nesting dolls whenever she "visits" the studio. She knows to be careful with them and she is usually good about not touching my stuff, but I will admit the other day she had all the dolls lined up on my tape measure to see how long they were and then they were having a concert using my bendable bright light as a spotlight for their "stage" which happened to also be my sewing table.
Your little guy is much younger (and oh so cute!!!) and I realize his attention span is probably pretty short, but maybe a special basket of toys for the sewing room might help. And there's also that "other" babysitter -- kids shows. A little bit of Elmo playing in the laptop DVD player has its benefits! But you're doing everything right -- moving all the sharp and dangerous things out of reach. It's amazing how fast they can find the sharpest thing in the room!
The only other thing that I found that worked was waiting until nap time and bed time.
Good luck!