I guess this is a problem only in USA. In Europe, the education is inexpensive enough with government funding and some effort from the child(which eventually pays back). Holiday vacations are usually for the whole family or organized by the school so this is planned expense. And in my opinion most of the expensive "toys" are usually not good for the child, like giving a sever year old an iPad/iPhone. I prefer to go with toys that spark creativity which usually are less expensive. That is not to say I would not buy expensive toys, however I believe that they should be given as rewards for memorable achievements or and to teach them what investment is. However I do admit that during the first five years the expenses for a child are huge, because most things have very short utilization lifespan - strollers, clothes, furniture, toys etc.
Instead of shared money with personal allowances, which works in constricting manner, we have shared goals approach to which we contribute whenever and however we can, which works in contributing manner. And we try to keep our budget aligned with our forecast for the goal or we reevaluate the forecast in case of unforeseen circumstances like the COVID pandemic. Of course we don't hit all of our targets but with time we get better at evaluating. Also any unspent money from a missed goal start as base for another goal.