Child account investment options (EU)

So, having two little ones, I decided to set up investment accounts for them.
The idea is that these would be focused on long term buy&hold (mostly dividend growth stocks).

Since I live in Austria/EU, the resources online are scarce, and I was wondering if anyone has some helpful advice on how to go on about this.

Several issues come to mind:

1. Does the broker location matter for tax purposes on dividend income?
2. What account type would be recommended for this purpose?
3. Does the equity location matter for tax purposes on dividend income? (i.e. is there any difference between dividends coming from US and EU companies)
4. Is there any type of account/scenario available to EU citizens where the dividends would not automatically be subjected to US witholding tax, and additionally, EU-state tax difference on top of that?
5. Anything else I forgot to consider?

From what I gather, the abovementioned taxes are unavoidable for EU adults, but is there any option that "forgives" this taxation for children? (even if it has attached constraints)

In general, I see plenty of good options for US citizens, but can’t find almost any information for EU.
Any help would be appreciated.