I'm from France. That is a good idea about the presents to be made by the kids, though I will feel bad as he gave a bit of money. On the other hand he could have done an activity with the kids and given it to me.
I have already done a collage with kids' photos for his 35th birthday. I'll ask the kids what they want to do as it's their father and if they want to buy something for him then so be it. Usually I orientate their choice but this time I'll let them decide so ex will see that there is no input from me.