You haven't failed, at all! The main thing is keeping yourself healthy overall, and your family and friends are right -- that means first focusing on your sight, and then focusing on weight loss later. I agree with luckymommy
about the walking -- can you take it slow? And the hula hoop was a great idea.
Gaining back 10 pounds, considering that you had to go to very minimal exercise, is not a failure, at all! Personally, I came back to 3FC probably about 40 pounds heavier than when I first joined! And it wasn't because legitimate health circumstances limited my movement... I was just lazy and didn't do what I should have done! That's totally not your issue here!
At any rate, I really, really hope this surgery works out well for you!! Hope that all will be well with your and your sons.