2.8yr old DS speech problem

[Dominique07]

Hi,
My 2.8 yr old DS is on the waiting list for SALT.

I know exactly what he has problems with;
There are specific sounds that he cannot say
such as g
and c

and if its a word with those letters in he remembers and fluffs up the entire pronounciation of the word.

Also he doesn't seem able to speak in very long sentances i.e. he'd rather point to something and say "peeeese" rather than ask for it. "NOT" or "NO" will replace a number of possible phrases, it could mean there is no more milk, I don't want anymore milk, it is too hot, it is too cold. etc.

He babbles a lot and talks to me very seriously and it is quite frustrating to him when I can't understand what he is saying.

I think most of his other behaviour is quite typical for a 2 yr old boy although currently he is developing a shy mannerism of dipping his head down so he doesn't have to say hello when meeting new people (although he can say hello). Does anyone know what this problem might be, or where (online maybe? Is there a website?)I can get some activities to help.
Obviously we do lots of reading and singing at home and I have always been focused on his language development right from the start so I feel a bit cross when people automatically assume I haven't been trying to help him talk, "Oh you shouldn't just guess what he wants before he asks for it" and other equally helpful comments!