Re: mouth inflation. If you use a pump (I do) you give them a bag of air. If you mouth inflate you hand them a bag of germs. Which do you want near a child's face?
Good point. I often ask the people hiring me which they would prefer. Often they don't care. If you do choose to mouth inflate make sure you are as healthy as can be. Take vitamins daily, eat breakfast, and exercise. Cancel ANY job if you feel like you are coming down with something.
If you want to use a pump that's fine. If you try to mouth inflate and have a hard time with it, don't do it. Mouth inflating is hard but if you get to the point where you feel comfortable with it and feel you do it faster than using a pump, then you might consider mouth inflation. Right now I mouth inflate mostly. It is a lot faster and more fun for me but if I were going to grt an electric or floor pump, I might go with that.