We have this in Poland. It's a big wealth transfer from productive responsible people to those who have a lot of children regardless of their economic situation. I think there are two problems with it:
-People who wait with having children till their situation stabilizes are now subsidizing those who don't. I think this is simply immoral and will result in more productive/responible/better educated people having even fewer children.
-the money goes to often dysfunctional parents and is spent on pointless consumption and alcohol. It's not a meme that if you want to see a lot expensive brand clothes or shoes you just need to visit a poor part of the town (I live in a very homogeneous country so no race/religion/culture undertones there).
I would much prefer the money to be spent on infrastructure making life better for the kids. Making sure children can get quality food, educational materials, help from social workers, can spend quality time outside of their dysfunctional homes and maybe get exposed to different ways life could be would be in my view way more helpful.
Making sure preschool children have their needs met is a more difficult problem. Still I think giving people free access to quality nutrition, clothes, medical care, toys etc would be a better way.
Sure there is a % of people who w can manage money and prioritize their children but those people would do well anyway if the money came as free stuff you can get for your children instead of buying it yourself.
Since (very modest for western standard) ubi like program was introduced we have seen huge raise in tourism and alcohol consumption. The numbers are there. It's just people who end up in bottom % economically are usually very bad with money and decision making.
I guess we can live with that one we can afford ubi for everyone but for now the priorities should be about giving children of shitty parents a fair shot at life. Good unfortunate parents will be able to use other programs as well.