If my husband is still alive but I die, can I will my kids to my parents?

my husband is terrible with money and other domestic matters, admittedly does not enjoy caring for kids and is active duty army so he is deployed a lot. If I were to die, I would want my parents to gain custody of my two girls (one is his step-daughter and the other is his) They have immense love for my girls and they have money so they could provide so much better for them than my husband ever could. Would a living will suffice in this matter or would I need to specify my wishes in another way also?