If you want to use a blanket, tuck a very thin blanket under the mattress at one end of the crib to keep it from moving around. (babybargains.com)
Plan for extra sun protection too with car window sun shades or thin blankets since the canopy may not extend fully enough. (bestcarseathub.com)
A child feels most safe and relaxed when he is cuddled and kept close, use thin blankets to wrap them up and place them close to your chest, you can also try a sling strap to stimulate the experience. (newkidscenter.com)