1- I start on pinterest. I look for the things that are practical, easy to make, will be an activity or add atmosphere. Above all I look for things that are cheap and easy to make myself. Then I pick 2-3 ideas that I think I can accomplish in the given time and will fulfill my criteria.
7- Bringing stuff home. Goodie bags are NOT required. Sure they are fun the kids like them, but they cost a ton and honestly everything in them are thrown away after 2 days. Alternatively, if you feel that you need to send guests home with something consider some of the following, one single fun item value $1 or less per child (small bottle of bubble bath, bows for girls toy car for boys, grab bag/treasure chest pick a toy out of, tumbler character cup). We have a tradition of doing a pinata. I fill it with candy and give each kid a ziplock bag. When the pinata breaks they run and fill their bag with candy and that is there "take home" gift. Nice thing about pinatas is they can take a long time to break if you have a talented person holding the rope and if your pinata is well made.