Child of Light is coming to Vita on July 2 in Europe. While there's no word yet from North America, PSN tradition suggests it might hit on July 1. [Update: Sure enough, it's July 1 in North America and digital-only, and the asking price is $15]
In the UK the Vita port costs £12 on PSN, and it's also getting a boxed copy that includes all additional content including a bonus quest, a new character, and a collectibles pack. We've confirmed with Ubisoft UK there is no cross-buy or cross-save functionality between the existing PS3 and PS4 versions and the new Vita release.