I remember when I was little we usually started early in the morning from Bohinj, as my family is from there. We reached Triglav during the day and then worked our way down to reach Bohinjska Srednja Vas in darkness, as we were very late.

Two days, or even a three--day hike is wonderful! And you have many places where you can stay for the night (not Holiday Inn, mind you, but very nice places for hikers to sleep with good cooking, typical for the place): Vodnikova koca at Velo Polje, Trzaska koca (provided you use Trenta as your starting point), Kredarica - the closest one to Triglav, Stanicev dom (very near Kredarica this one too). Koca, pron. kocha means shack but You can also use the name dom which literally means - home. These are the usual names for shelters here in Slovenia.

Hiring a guide is perfect. And of course I would advise you to wait for late spring and summer to start hiking so the month of June is really a good choice. All you have to do is choose which way you want to choose to reach Triglav. It all depends on personal preferences and of course on how much time you want to spend in the mountains.

Hope that helps you with your planning.

Goran in Nova Gorica Slovenia