Section 172 (3) only.

In Oct / Nov, I recieved 2 speeding fines for doing 36 mph in a 30 zone on 2 separte occassion. The car is registered in my husbands name so we filled he filled in the relevant paperwork and one of the fines came though which we paid and delat with. We were in the middle of moving house so things were a little disorganised and whilst going through paperwork a couple of weeks ago I came across one of the NIP's that was to be completed by my husband, we filled it in a sent it off only to recieve a court summons on Friday. Shall we just pleased guilty or add some mitigating circumstances. What will happen? We have a baby on the way and not much spare money and are not sure what to do next. This was a genuine mistake. Any advice would be gratefully recieved.