I made a one click solution.
Well, then you may be causing issues later.
If you're downloading SVN zips (which you've asked lead4U to do, convert to SVN so you can do that), and then RE-distributing them in a collection, when an addon author goes to update (via svn, or workshop like I recommended), your collection is then out of date. Worst case, it has exploits or major bugs. Best case, it's just missing a model/sound or two.
You should really get/setup a fastDL if you're going to use addon packs that have additional items in them.
Then you just keep your server and DLcache up to date, Gmod clients do the rest.
If not that, then have them download an HTML file with links they can click on to direct them to the SVN and Workshop subscriptions (or here, if you're using releases only available here).