I would definitely advise you looking carefully and being able to discuss both poems for Skrzynecki and the belonging question. This is because only preparing one leaves you with a problem if the question does not suit that poem. Both of the poems have really clear links to "The China Coin", with "Feliks" allowing you to discuss links to the book about family relationships, the lack of desire to acknowledge a particular heritage and the idea that there are barriers, or problems to belonging. "Postcard" gives you the opportunity to write about these, as well as the way that attitudes to belonging can change over time and that individuals see a need to form strong links with heritage in order to understand their own identity. My opinion would be that preparing both lets you have a choice. They are terrific poems and both have techniques such as the use of imagery, first person voice, fairly simple language, distinctive tones, that give you plenty of opportunity to demonstrate a thoughtful, detailed understanding of the Area of Study.