We were told dd2 was unlikely to be verbal due to her oromotor issues, so we had a Big Mac/ little Mac when she was tiny (to get the idea of reciprocal communication) and then she was started on makaton. (I found the idea of makaton hilarious, as her fine motor was abysmal, so it was impossible to work out what she was 'saying'). She didn't sign for a long time, but then would use it to join in songs and communicate for snack at nursery. The makaton seemed to give her the impetus to communicate.
She started to speak about 3, 3 1/2, but was v dysarthric. She was statemented for communication, and a few times school called me as she had got herself upset and no one could understand her - mostly it was about working out the context and guessing until you got it right!! She's 9 now and v clear (well, in comparison!) she is able to self correct (swallow, use her lips) to improve clarity if someone doesn't understand. We do still get the odd comment from school that they find it hard to understand her at times, but she has been discharged from slt - essentially, she is now as clear as it is likely that she will get, as the issue is neuro-based. So any further issues are for school to cope with, not for dd2 to try to improve iyswim...
There are tons of slt exercises... All of the licking, blowing, to mouth aerobics etc. once dd2 was speaking, we used the Nuffield verbal dyspraxia programme from around 4yo.
At 2, it's about finding a communication method that works, that can hopefully be transferred to nursery/ school in time. Does he have a specific iPad app for comms?