concerns for a 2 and half yr old

[Natternic]

my concerns are I cannot understand a word he says, he babbles away. You can understand the odd word occasionally. I talk to him all the time asking him to make choices -toys/snack but he just looks at me blankly. He can however carry out a simple instruction - put shoes in the box.
He chants the alphabet and counts up to 10. He recognises numbers. He knows the name of many car badges - bmw, honda, volvo.
He cant seem to climb on to a ride on car, gets stressed out if you place him on a bike/trike, has no interest in playing with anything but toy cars.
He smacks other children, I put him in naughty step doesnt respond to this.
He doesnt want to get out of the buggy when at the park, library anywhere, if I attempt to he just screams and kicks.
Today he seemed really stressed and cried at lunchtime, till i worked out he didnt atually want any lunch,so told him he can go play.
He hasnt had his health check yet, obviously I will be doing my report on him to pass to parents, Ive spoken to the health visitor and they say I should talk to mum and encourage her to call the health visitors.
I am no good at this type of conversation.
Please help

[hectors house]

Is he the only child, if so maybe mum hasn't got any idea that he has a speech problem and that he doesn't play like a child his age should.

Be careful how you bring the subject up as I had a friend who had no idea that there was anything wrong with her daughter until she failed her 3 year check up and was really upset that she hadn't realised.

How long have you looked after him?

[mabel]

I had a girl very similar she was 3 last November and speech was poor but I have done loads of one to be with her and she is really coming along.....

She is bright and knows lots just poor speech