I have difficulty with some kids at this age to produce /k/ and /g/ and they don't have a repaired cleft. Unfortunately, velars are just not going to come in UNTIL the child is ready. In the meantime, is there something else you can work on ?
Each session for about a minute, I would stimulate final /k/ using the tongue depressor in VC combos ack, eek, ike, oak, ook.
I would avoid final /g/.
For most kids, this exposure works well and they are able to get some good productions in about a month or two. However, with the repaired cleft, it might take longer.
Be sure to start focusing on other sounds in error in therapy as you might be able to fix them before /k/ and /g/ begin to even emerge. I sure have found this to be true over and over again