You could make a custom rss feed…..
Here’s a link for that
http://yoast.com/custom-rss-feeds-wordpress/
Simply use that info to make a page template
Make a new page through the WP interface and assign that template
The url for that page is your new feed.
You just need to adjust the query line to call to both tags
For instance, I have a hockey feed, my custom post type is col_avs, I’ve adjusted my query like:
$posts = query_posts('post_type=col_avs&showposts=".$numposts);
You can see it in action at http://www.rvoodoo.com/hockey-feed
It goes to a feedburner feed, but that feed is generated using this method