As a true tale that might calm you a little :
My DS2 had NO words at 3yo. Wasn't even really babbling. He had been put on the waiting list for SALT at 18mo (through NHS, private not a financial option). He said his first word (Mum) at 3y5mo.
I had been through SALT with an older DC (partially deaf so speech delayed), and used all the techniques I had been shown with her for DS2.
By the time DS2's first SALT appointment came up, he was aged 4y5mo, and almost in Reception. By that point, he was speaking mostly understandably, with some mispronunciations, and very unusual syntax, but still, he could carry out a mostly understandable conversation with you.
Now at 8y9mo, he could talk the hind legs off a chuffing donkey, he never shuts up! I often say that he was a slow starter, but my goodness is he making up for lost time!
Occasionally when my ears have taken enough battering for one day, I tell him to 'Shush!'. And then feel incredibly guilty because once upon a time I feared he would never talk.
The extra 9 months wait for speech therapy will be less of a problem to your DC's than a stressed mum needing a holiday IMO. A more calm and rested mum will mean a mum that can put more time into developing their speech.
The majority of DC's with Speech Delays DO catch up eventually. If they understand what you are saying to THEM (following a simple instruction like pick your ball up), then that is GOOD.
You may also find that twins ARE slightly later talking, simply because they can communicate between themselves in other ways.
Also, has their physical development taken a massive jump over the 5 months that they don't seem to have acquired new words? If they have learnt how to jump, how to pedal a trike, how to climb stairs properly, how to do forward/backward rolls, how to feed themselves effectively with their cutlery, have been working on potty training, you might find that they take a massive leap with their speech in the very near future.
I have seen, quite often, in my own DC's and my friend's DC's, that speech will often take a back seat whilst a child is developing their physical abilities, and then it suddenly 'catches up' to where it should be.