Worrying about transition to Universal Credit...will I receive less?

Hello all,
Someone mentioned to me today that Universal Credit will start to replace a lot of benefits going forward and that you may end up receiving less per month when the changeover happens.

I tried using the calculator to calculate how much I would get but I am getting a bit confused using it as the figures it is providing do not seem realistic.

We currently receive the following benefits per month:

DLA: £224.00
Carers allowance: £248.00
Child Tax Credits: £605.00
Child Benefit: £137.00.

We have an autistic son who receives DLA and my wife gets carers allowance for him.

Is there any way of being able to tell by how much our benefits would go down by when this change happens and is the change to Universal Credit expected to happen in 2017 for most people?

Any help much appreciated.

Cheers