~~Moved to AOS Family K1/K3 P&P, from Moving Here and Your New Life- as the OP is asking more AOS related questions.~~
Mod Hat off
Regarding the name changes, the marriage certificate is what allows your wife to take your name. Sadly your Step Daughter cannot do the same. It requires a court order for name changes. Now I'll let you know about my friend's experience. They never legally changed their kids names, but they did use the "new names" on everything for schools and doctors. They all had the name listed in the files but had a sections on the forms saying goes by (insert name).