.js

var queue = [],
    output = [];
    
function add(args) {
    queue.push(args);
}


function delay(n) {
    return new Promise(function (resolve) {
        setTimeout(resolve, n);
    });
}
function process() {
    if (queue.length === 0) { return; }
    return callAc(queue.pop(), [
        'FormattedID',
        'Name',
        'Children',
        'Parent',
        'TeamMembers'
    ]).then(function (result) {
        result.Object.Results.forEach(function (item) {
            output.push(item.Name);
            queue = queue.concat(item.Children._ref.split('webservice/v2.0')[1]);
        });
        return delay(1);
    }).then(process);
}

function callAc(ref, parameters) {
    return restApi.get({
        ref: ref,
        fetch: parameters,
        scope: {
            workspace: '/workspace/XXXX'
        },
        requestOptions: {}
    });
}

add('/Project/<some_project_id>/Children');
process().then(function () {
    console.log(output);
});

awesome..