Hi. My name is*****'m looking at your question now and will post my answer or ask for more information here in a short while.
You should keep a record of gifts you make whether they are joint or not. As you and your wife each have your own nil-rate bands, then you should specify who makes any particular gift. Joint gifts by parents are normally seen as being made on a 50:50 basis but that's not always the case. You can find a list of exempt gifts here.
I hope this helps but let me know if you have any further questions.
I'm just following up to find out if my answer helped or if you have any further questions.