I would love to give you some more ideas on how to help Alex develop more language. It's so exciting that he is already using two sounds to communicate with you - it shows that he understands the power of his sounds - that's a powerful and important first step. It's wonderful that you're celebrating his sounds to show him the power of his speech - we find it's really important to celebrate any sounds that children are already making. This will help him continue to be motivated to use his voice and talk to you more.
Here are a few ideas to add to what you're doing:
1) RESPOND WITH ACTION to all of Alex's sounds. When he makes ANY sound at all, DO something for him that he would really enjoy - get him something fun from the shelf and do something silly with it (e.g. get a puppet and tickle yourself with it), tickle him, sing for him, do a dance for him, wave a bunch of colorful scarves around so he can watch them move, etc. Do something motivating for him so he can see how much he gets from speaking.
2) When asking Alex to speak, make sure that he is MOTIVATED for interaction with you first. It's important that you establish a fun game that you can play together so that he's speaking for something he wants, vs. only speaking because you ask him to. (For example, once you've tickled yourself with the puppet, and he likes this, do it again and again FOR FREE so he can see how fun you are to play with. Then ask him to say the word tickle when he's motivated for what you're offering )
3) BREAK DOWN THE WORDS into more manageable pieces for Alex. Speech includes a LOT of details that we take for granted - getting your brain to think of the correct word, sending that message to your mouth muscles, getting your muscles to move in a coordinated manner so they can shape the word, getting your breath to go out at the correct time to match your mouth movements, using that air to create SOUND in your throat to say the word... It's a LOT of work to speak! So break it down for Alex - when modeling the word "bounce" - break it down to just moving his mouth to close his lips together... Then ask him to make the "b" sound... Then ask him to open his mouth... Then ask him to make the "ow" sound... It may take time to teach him all of the pieces - but if you help him break it down into more manageable bits of information, he'll find it easier to speak.
4) BELIEVE in every moment that Alex can speak - because your belief in him will help him speak when it might be really challenging for him to do so.
Feel free to respond with more details about your son so we can continue to answer your questions - and have fun helping Alex!
Son-Rise Program Teacher
The Autism Treatment Center of America