I for one find it very difficult to understand how one can still maintain relationships once there has been a split, in my humble opinion a split should mean just that,these things can never work ,when you have split from one and then found another ,you must be able to see it from your G/F perspective ,all this opening Xmas presents etc how long should this carry on for ,this is not good ,I am not a jealous person but I am getting wound up just thinking about how generous you feel you are with your time for your EX, please remember she is just that she is your ex ,I think that your new relationship should take priority,no matter how pleasant you might think your ex is to your G/F,you should know by now females and males are wired differently that is certain it is well documented.
You could split from your present G/F only to find the same thing will happen with the next one .The result will be you will end up on your own ,your son reaches the age where he limits contact has his own friends relationships ,your wife has her relationships and you will still be on your own.
I obviously have NO REAL idea of your true situation,these are just ramblings throwing a few suggestion into the mix and just see if you can make any sense of it all.
Kindest Thoughts In A Mo