I hadnt realsised that you hadn't got a flight to Ljubliana in which case you are rather stuck. A bit of a drag getting there and I'm unsure if there are still any packages left at this time of year -which as suggested above is the best idea.
however, the best alternative is Easy Jet with daily flights ex Stansted with resonable prices if booked ahead, and at at good connecting times for the Dublin -Stansted flights with Ryanair.
But you must must must give yourselves at least a couple of hours between flights because if you miss a connecting flight you're on your own.
You could, if you like scenery and a bit of interesting travel, go one way to Ljubiana and one way via Klagenfurt(Ryanair Stansted and I think somewhere else in UK) But you must stay in Klagenfurt for a day or so and look around -WortherSee etc.
There's a train from klagenfurt that goes within a couple of miles of Bled- may need a change at Jesinice.
Easy Jet is best way but Klagenfurt suggestion adds a bit of fun.
You need to study Klagenfurt flight timings to see feasability of this idea.