If you're booking a package reservation with at least 1 day tickets for the adults and the 5 year old, then yes you can.
If you're an annual passholder, a DVC member booking through member services, or eligible for the military room discount, then you can get it without the tickets.
The above poster makes a good case for you to think about, since you have 4 reservations that would require 5 credits. On a 3 night stay, you'd have 3 TS credits on the regular (you'd have to pay for the equivalent of 2 credits) and 9 credits on the deluxe (you''d have to spend 4 more credits.)