WASHINGTON — I’ve always struggled with how much financial freedom to give my children.I’m a lifelong penny-pincher, and I wanted my children to embrace frugality, too. So I forbade certain spending. I didn’t want them to grow up being spendthrifts.But as I’ve matured and gotten better at parenting, I’ve realized that sometimes I have to let my children make financial decisions that won’t be wise.Even writing that makes me grimace.When it comes to their money, should parents let their children learn from their own mistakes?For the longest time, back-to-school shopping for my three children created a lot of stress for them and for me.