You perhaps alread have the information listed below but if not then it may be a help in connecting the Sleigh, Kenniwell names and Edward.
I searched using Keyname Search at the NSW State Records Website.
Child Protection and Care Index - SelectSurname FirstName Age Petition Date Committal Date Date of Discharge Remarks Citation Institution RecordType Name: SLEIGH Edward age:14 yrs Committal Date:08/05/1826 Remarks: Mother: Elizabeth KENNIWELL. Petitioner: KENNIWELL, Elizabeth. Parent or guardian requesting child be returned to their custody Citation: NRS 783 ; Reel 2776, Page 033-034 Institution: Orphan Schools Record Type: Applications for children out of Orphan Schools
Name: SLEIGH Edward - Committal Date: 10/07/1821 Remarks: Mother: Harriet SLEIGH Citation: NRS 898 [4/7208]; Reel 1477, Page 007-008 Institution: Male Orphan School Record Type: Col Sec Special Bundles: List boys received
Name: SLEIGH Edward age: 10 yrs Committal Date: 10/07/1822- Remarks: Citation: NRS 796 ; Reel 2777; 1477, Page 004 Instituation: Male Orphan School Record Type: Admissions book
SLEIGH Edward 10 yrs Committal Date: 10/07/1822 Remarks: Mother: Harriet SLEIGH Citation: NRS 796 ; Reel 2777, Page 004 Institution: Male Orphan School Record Type: Admissions book
CONVICT INDEX SLEIGH Harriet Ship: Maria Year: 1818 Number: 28/657 Record Type: Ticket of Leave Citation:[4/4069; Reel 911] Remarks: District: Wallis plains
SLEIGH Harriet - Ship: Maria Year: 1818 Date: 20 Nov 1837 Record Type: Recommended Conditional Pardon Citation:[4/4478; Reel 797 Page 082] -
Harriet Sleigh is also mention on the Convict Conditional Pardon Index.
KENNIWELL George Ship: Isabella year:1818 Number:34/541 Record Type: Ticket of Leave Citation:[4/4094; Reel 921] Remarks: District: Williams River; Tried: MGD