Well for a start, not wanting pain from SPD is NOT a selfish reason. How hard is it on your kids to have you in pain and not able to do stuff? That sort of thing affects everyone including you so you can't write that one off as selfish. Wanting to get fit and healthy? Again, not selfish. I could go on but.....

At the end of the day it is up to you and what you feel that you and your family can deal with - it needs to be a balanced approach and look at all aspects financial, emotional, psychological, physical, logistical etc. Only you and you DH can work out what is best for you and the kids. All reasons are perfectly valid if they impact your family.