Compliance interview HELP

Hi, I'm not sure if anybody can relieve my anxieties but here's hoping so.
I today have received a compliance letter saying they are reviewing my benefits and circumstances. Firstly, is this done randomly or has some spiteful person been stirring goodness-knows-what. My anxiety is through the roof to say the least.
I have been claiming benefits for a few years now but my circumstances haven't changed, I claim IS, CA, HB, CTB, CTC and my children and hubby are on DLA &PIP respectively. My husband is also on ESA (contribution based).
We had a benefit review done by the Citizens Advice a couple of months ago which showed we were actually owed money- could this have triggered this 'interview'- we know Citizens Advice have funding from the DWP?
Also, I will be away on the date of the interview- I have arranged to take my disabled son away for a few days, it was booked and paid for a few weeks ago so can't be cancelled without losing money (and causing huge upset to my son). does this count as good reason for re-arranging the interview?
I haven't stopped shaking since I opened the letter, everything I have googled seem to point to 'fraud' and very few seem to be randomly sent. One website talks about DWP targets and clawing back money? My son was randomly selected once and he doesn't even claim benefits- it was from an old claim! Or could it be a simple review as to be fair I haven't had an interview with the DWP for a while and that was for carers allowance about 2 years ago.
I know the wording on these letters is significant, it doesn't mention any benefits in particular- I am a full time carer for my husband and haven't worked in 6 years. The only income we have coming are benefits and the only lumps sum payment I've had in the past were benefit back-payments- I didn't see it as significant as it was all benefit related and surely the DWP would be aware of it? Can you be penalised for receiving a lump sum benefit wise?
Due to the amount of benefits coming in at different times our bank account balance fluctuates but as far as I'm aware doesn't go over the lower savings threshold let alone the upper limit (I wish)- nowhere near! I don't check the balances on a daily basis but have a general idea of whats going in and out.
Things are stressful enough caring for my husband and my disabled children, this has spiralled my stress levels to astronomical proportions, all we seem to have done over the past few years is battle with the DWP, I hate relying on benefits but circumstances dictate that for the foreseeable future that is our life.
If the truth be known I should be claiming PIP due to my severely declining health- even a family support worker has encouraged me to do so- but the stress is too much for me to consider. I feel so swamped
Any advice would be gratefully received.
Thank you in advance.

thank you Gordon, still cant eat or sleep going to CAB office tomorrow and hopefully they can ring for me , my head is all over the place so I need an impartial person's help.
Hopefully will know more then.

Hello Ceri,

My flatmate was invited to one of these a year ago and they played the game of it being just a random check. Cobblers it was a fraud interview where they accused him of living as man and wife with me. We are not but it took a court appearance to sort it out.

I am not trying to frighten you. But take this as some perhaps some good advice. They will probably not record the interview but at the end ask you to sign at the bottom of the interview form. My flatmate ( who has mental health problems, that's why they chose him to interview not me ) asked if he could have a copy of the form as was told yes. He signed it, without really looking at it as he thought he could look at it later with me. Once he had signed the compliance officer whisked the form away and refused to give him a copy and virtually bundled him out of the room.
He did not see this form for two year until he got it just before his appeal, virtually on the steps of the Court. When he did it was a pack of lies, but they said ' well you did sign it'

So do not sign this form. Say you wish to make a written response later after talking to your husband. Ask for a copy of the compliance officers form there and then and if refused ( which it will be ) say whats sauce for the goose is sauce for the gander. Do not be conned into being told there is nothing to worry about or that you have somehow passed the test.

Yes this will cause trouble for you and probably more interviews but that is better than asking and worrying for two years like my flatmate

Beragon