Those seedlings are young enough I would not worry about some side growth right now. Just keep checking them each year and prune or stake as needed to get straight trees if that is what you desire. In 10 to 20 years, with the trunk diameter much bigger, a lot of that crookedness will be absorbed. The cages will help a lot too. Just look out for neighbors planting 'maters in your cages !!
/ Need advice on the small white oak trees I planted last year.
Someone mentioned the tubes.
I have used both the blue-x and tubex.
If you have deer in your area go with the tubex at 5'. Its what I have in my crep planting to keep the deer off.
Blue-x are recycled x-ray films pain to use and break down after a few years. Once I can take the tubes off my trees, I have some oaks that are 7' high now after 2 years (I bought 2' plants to start with), I will be able to use them to replant different areas in my forest.
/ Need advice on the small white oak trees I planted last year.