evernote - Convert Evernote Markup Language (ENML) to Markdown with pandoc

Question

I'm trying to convert Evernote Markup Language (ENML) to Markdown using Pandoc. ENML is mostly a subset of XHTML with a few additional elements. The element I'm trying to convert is a special <en-todo checked="true"/>. Here's a sample ENML document with two en-todo items:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE en-note SYSTEM "xml/enml2.dtd">
<en-note style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">
  <div><en-todo checked="true"/>This is a thing<br/></div>
  <div><en-todo checked="false"/>This is another thing<br/></div>
</en-note>

I'm trying to convert it to the following markdown:

[X] This is a thing
[ ] This is another thing

My current approach is to create a JSON filter

pandoc --parse-raw -f html -t json test.enml | \
      ./my-filter | pandoc -f json -t markdown

I'm not sure how to properly parse the RawInline blocks:

[
    {
        "Para": [
            {
                "RawInline": [
                    "html",
                    "<en-todo checked=\"true\">"
                ]
            },
            {
                "RawInline": [
                    "html",
                    "</en-todo>"
                ]
            },
            {
                "Str": "This"
            },
            "Space",
            {
                "Str": "is"
            },
            "Space",
            {
                "Str": "a"
            },
            "Space",
            {
                "Str": "thing"
            },
            "LineBreak"
        ]
    },
    {
        "RawBlock": [
            "html",
            "</div>"
        ]
    },
    {
        "RawBlock": [
            "html",
            "<div>"
        ]
    },
    {
        "Para": [
            {
                "RawInline": [
                    "html",
                    "<en-todo checked=\"false\">"
                ]
            },
            {
                "RawInline": [
                    "html",
                    "</en-todo>"
                ]
            },
            {
                "Str": "This"
            },
            "Space",
            {
                "Str": "is"
            },
            "Space",
            {
                "Str": "another"
            },
            "Space",
            {
                "Str": "thing"
            },
            "LineBreak"
        ]
    }
]