What's the best alternative to chemical based anti-mosquito lotions for toddlers? Any good brands? DIY solutions don't work out for me since they easily spoil and they are hard to prepare.

Try citronella oil. Since it's an essential oil, you may have to need a carrier oil like virgin coconut, olive or sunflower. Or better yet, try to get some organic bugs creams. I suggest you try Human Heart Nature's anti-insect spray and Coco Haven's Bugs Away Cream. :)