Asking for a ruling on a point of style like this is generally pretty futile in English. There is no central authority. However, style manuals or internal style sheets can provide guidance, even though different ones will have varied answers.
Which answer you use depends on what document you're writing, and whether there's a style sheet that covers it. (Many corporations have internal style sheets.) If the document you're working on is to be published, one of the following general style guides (i.e., not an in-house, corporation- or publication-specific guide) may help:
The closest to a solid ruling on this that I found is in the Franklin Covey Style Guide for Business and Technical Communication. Vertical lists use bare numbers followed by periods, with sub-entries using letters in the same format. Inline lists use numbers/letters inside a pair of parentheses: (1), (a), and so on. (1997, pp.158-160)
APA style uses numbered lists without parentheses (see Quick Answers - Formatting lists and pairs of brackets in an inline list (see Lists, part 4):
In running text, a series of items is designated by letters in parentheses: (a) first item, (b) second item, and (c) third item.
The Chicago Manual of Style uses mix of bare numbers and letters, as well as items enclosed by a pair of parentheses as well as a single parenthesis, leaving the exact execution up to the writer/editor. (16th edition, CMOS 6.126 Vertical lists with subdivided items (outlines) - that's a subscriber-only link, I'm afraid.)
The web-centric Yahoo! Style Manual, on the other hand, barely discusses numbered lists at all, assuming that lists on the web will generally be bulleted. However, the entry on lists does have an example of an inline list (embedded in the text of a paragraph) with opening and closing parentheses.
I also consulted The Economist Style Guide, which uses no special formatting for lists (and doesn't even put a period after the numbers in a vertical list). The Copyeditor's Handbook is also silent on the issue.
If you're writing for internal or informal documents (emails or such), just pick a method that appeals to you and stick with it. Personally, I prefer using single brackets in vertical lists and double brackets in inline text, since you're reading up to them; but that's just a personal preference.
And one last thing: Smiley faces at the end of a parenthetical sentence will be awkward no matter how you handle them. I suggest rewriting to avoid this.