this is a personal choice that YOU have to make, no one else. like someone said, due to your previous questions, it sounds like pregnancy is really hard on you, and you already have four children. do you plan on having more? we are done, and i am fine with taking the pill. is it really so inconvenient? i never thought about it, just part of my life.
you don't HAVE to have surgery, to avoid more children.
you don't HAVE to gain a lot of weight, if you do have the surgery. who is to say that the surgery even caused their weight gain??? many, many people are overweight. and all my inlaws are overweight - most of my family too. so that seems a silly argument to M.. people are fat all over, for all kinds of reasons. if you take care of yourself there's no reason for you to gain a lot of weight. it should not factor in your decision, imo.
weigh YOUR reasons. discuss it with hubby. then YOU make the decision. you are always allowed to change your mind later (assuming you don't do it right now, i mean). let it be YOUR choice and be comfortable with that. then just tell them, "well this is what's working for us, so we're good with that." don't take it as judgment that they feel this way - it was what worked for them. you have a right to decide whether it will, or won't, for you.