That's your call about delaying. You need to get in touch with the council and see when they offer citizenship appointments as they may only do "last Thursday of the month" type of appointments, for example. Personally, being a bit of a pessimist, I wouldn't take the risk having the latest appointment you can possibly have. You could get ill, car breaks down, train gets cancelled etc. But that's just me and likely just being over the top.
Jimbo travelled to the UK in this situation and my wife will be in three weeks also.