This is a good question to ask before purchase, because some orthopedic supports are designed for overnight wear and others are not. The 710–2 is meant to limit sharp bending and turning and to give the neck a calmer setting during shorter periods, and the product description does not cover sleeping as a regular use. During sleep, head and neck position changes involuntarily, and the wearer cannot adjust or reposition the collar, so overnight wear is a different situation from supervised daytime use.
Unless a specialist has specifically recommended overnight wear as part of a recovery plan, take the collar off before the child sleeps. The calmer rest periods mentioned for this product are better understood as rest while awake — for example sitting quietly or lying down during the day — rather than a replacement for normal sleep positioning.
If a specialist does prescribe overnight wear, ask them to confirm the fit for a lying position and the exact total wearing time, because a fit that works for sitting may not stay comfortable over hours of lying down. After any longer session, check the skin where the collar contacts the neck for irritation or pressure marks.