Disney counts every person, no matter how old, for purposes of assigning table size and for reservations. Technically you will be a party of six and most places will charge you the automatic gratuity. In my experience, occasionally a server won't put the automatic gratuity on the check when there are five people and a baby, or four people and two kids under 3. You should expect everyone to be counted, but occasionally a server is more relaxed about it. The tip is on your total spent anyway, and it's only 18% so, to me at least, it doesn't matter. I would tip that much or more regardless. What does bug me, is when they don't mention that the tip is included and then I tip again and realize later that I double tipped. That makes me mad. I know I should check the receipt of charges but sometimes I'm enjoying my family and friends too much to take the time out to scrutinize a bill and I forget about automatic gratuity.