DS1 is now 2years and 3 months old. He has heaps and heaps of words and can put together simple sentences like "dog in the car" "mum put on pants" "car on truck" head went underwater" and "I did a poo"

But his pronunciation is pretty poor. He uses the same pronunciation each time he says a word but at least 75% of this words bear little resemblance to the actual word - I've just figured out what he is saying if I see him pointing to the thing while saying the word. So for instance:
Ella = aeroplane
Hemp mee = cement mixer
bu tur = bush turkey
bee bee = biscuit
gah = stuck
boot = milk (possibly from bottle?)

And names of common people
doe = Josh
ra ra = Grandad
Re ra = Andrew
Aba = Sophia

Should I be worried or will this fix itself in time?

I'm the only one that can fully understand him - DH and the grandparents can pick up a few words.