Yes, it is possible ;) Finally I found a way to send DTMF tones via tasker automatically. You can use this trick with Tasker App Factory created standalone kid apps too.
Just use "," between dial number and DTMF tone.
For example; if you want to call 05395390530 and send 5 after 10 second from answer, you can call this number from tasker (with auto-call option selected): 05395390539,,5
Dont forget to use minimum a "," between each DTMF command. For example; 05392552070,,5,1
Good luck ;)