Wow, no evoker or conjurer at all? TWO illusionists? And all human?
That makes it more difficult. But still, doable. IF they work together that is.
For example, if the diviner figures out there are some opponents coming around the corner with detect thoughts, one illusionist can use silent image to create the appearance of a dragon, while the other can ready an action to cast ghost sound of a dragon roaring as soon as the first casts the silent image.
The Transmuter has got to get a decent Con score, because they will end up being the front line a lot. Alter Self into a Tren (see
http://www.wizards.com/default.asp?x=dnd/iw/20040613a&page=4 ), or something similarly powerful with a good natural armor and natural attacks, cast Bull's Strength and Enlarge Person on yourself, and you are buffed up to smash! Sure would be nice if the diviner could make some scrolls of true strike for the Transmuter as well.
But when it comes down to it, that combo of casters is all about stealth and subterfuge. The diviner can determine what situation you need to prepare for, and then the Illusionists and Trunsmuter prepare for it. Silent Image, Minor Image, Disguise Self, Invisibility, Alter Self, Rope Trick, and Spider Climb, are all excellent high-stealth / subterfuge spells that work best if you know what is coming and have a plan.
I once adapted a great adventure, Gorgoldand's Gauntlet by Johnathan M. Richards, into an wizard college adventure (actually more of an adventurer's college). It worked well for 1st-2nd level characters. It has a lot of puzzles and such, but still some combat (mostly nonlethal) to challenege the party. I could email that you if you are interested.