Do I have to get special empowerments to venerate Ksitigarbha and recite his name?
From what I have read and heard:
If you belong to exoteric Mahayana Traditions or none, nope, although the method of veneration would vary according to respective Mahayana Trads, especially in the East Asian context.
If you belong to a Vajrayana tradition, yes, because of Teacher and Lineage considerations.
I can still recite Guan Yin along with Ksitigarbha and dedicate merit right?
Yup, it's been my practice too for years now.
Here's a link:viewtopic.php?f=41&t=61
Personally, I have benefited greatly from this Dharma Door of reciting His Name and Sutra all these years and have seen and known many cases who have similarly benefited. He is greatly venerated in East Asian Buddhist Traditions, has a mountain shrine dedicated to Him in Anhui Province, China (Jiu Hua Shan - 'Nine Glorious/Flowers Mountains) and reportedly the second most 'beloved' Bodhisattva after Avalokitesvara Bodhisattva for Chinese Mahayana Buddhists, particularly those who belong to the Pure Land Tradition and He normally occupies the place of honour either below/in front of the image of Amitabha Buddha/Three Sages of the West (Amitabha Buddha, Avalokitesvara & Mahastamaprapta Bodhisattvas) or as stand alone surrounded by memorial/ancestral tablets/plaques in the Western Hall of Merits Shrine in a Chinese Mahayana temple. In Chinese Mahayana Buddhist liturgical calendar, He is honoured on the 30th Day (or last day, sometimes ending on the 29th) of the 7th Month, in the Chinese Lunar Calendar or September 7th 2010. His other monthly remembrances are as stated in the Sutra as per the appended link above.
Namo Kṣitigarbha Bodhisattva!
Namo Di Zang Pu Sa!
Namu Jizo Bosatsu!
Namu Ji Jang Bosal!