Going without a thief can be tough, especially for IWD. They're such a (somewhat) necessary evil. If it weren't for traps, I'd leave them behind. If summons could set them off, I'd be rocking a cleric and druid.
What about an all cleric small party (blades are overrated, blunts are king)? You can have a vanilla halfling cleric for a tank, a dwarf fighter/cleric for a striker, a gnome cleric/illusionist (necromancy is overrated in IWD) for spellcasting, and a gnome cleric/thief. Keep Con high on everyone for shorty saves and you should be coasting. Perhaps they are all clerics of Tymora.
Yes, I'd noticed that summons don't set off traps! What I also noticed is that it is usually possible to go round the traps, so all that you need is detect traps! Clerics have that! That is why I am trying a fighter/cleric. It probably won't work, but in trying it I will learn a lot about the game. The first law of gaming as far as I am concerned is "Enjoy the game!" Winning comes way down on my list of priorities!
I have reached the Kuldahar Pass. Fighter level 3, Cleric Level 4, Gold 1550. Better armour is my first priority upon reaching Kuldahar.
Getting there was more of a problem as I was repeatedly ambushed upon trying to rest. I ended up avoiding conflict as I proceeded.
After sorting out the inn ownership, I became a level 4 fighter.
I then took on yetis. I sometimes took on two at a time, but when faced with three, I fled!
However eventually I defeated the yeti chieftain and was able to return the heirloom to Mirek.
In the first four chambers in the vale of shadows I couldn't get around the traps, but the damage that they did was trivial. All I had to do was heal myself when I left them. About to start the last one. Level 5 Fighter: Level 5 Cleric. I have been using summoned skeletons beyond traps to clear the area before activating it just in case the trap incapacitates me. There was one trap which might have done that but didn't, probably because of shorty resistances.