This is a bit late, but...
Using timed explosives on the Array wouldn't have worked. Tuvok said it would take hours to get the "Send us home" program working an in that time they'd have been under constant attack from Kazon reinforcements stronger than the force they were already fighting. They'd never have lasted long enough to use the Array, so it was either "Blow it up now and leave" or "Stay, try to fight and probably lose so they'll get the Array AND Voyager and kill us all."
What's silly is that they acted like the Array was an option in the first place.
Uh, no.. as the episode presented itself Voyager had cleared out virtually all the opposition before the Array was destroyed. Three ships total were shown in the attack. Two of the standard small ones and the big one. The big one was destroyed when the Maquis raider kamikazeed it and Voyager took out one of the smaller ones.
What created the supposed time crunch was in it's death throes the big one crashed into the Array damaging it's self destruct. That's when Janeway elected to blow it up.
The time crunch didn't exist though. Think about it, what did the Kazon captain do after they blew up the Array? He sent a message to Janeway saying he was pissed off and left. If he had reinforcements at hand, he was certainly pissed off enough to have continued the attack, especially after the losses he took they'd want some revenge.
So they had all the time in the world. And if you re watch the episode Tuvok was instructed early on to learn how to use the Array. The reported that he had done so just when the fight had begun. So even supposing there's the "several hours" there's no Kazon around except the one small ship that had enough and was certainly no match for Voyager. Voyager's demonstrated the ability to scan and detect Kazon vessels when they are hours away so, any reinforcements approaching would've been detected as Voyager demonstrated it could do in several season 2 episodes. So the option of beaming over a bomb with a timer is very legit. Or if that somehow isn't reliable enough and Janeway is so self-righteous she can stay behind and pull the trigger herself.
Again, this is all as the episode presented itself. There was no time pressure, the Kazon had already been beaten when Janeway chose to destroy the Array directly. You can chalk it up to Janeway being dumb and/or bad writing. A simple line suggesting reinforcements were approaching would've resolved this, heck have the Kazon board the Array and directly tempt Janeway saying "If you leave us alone, we'll use it to send you home" and have her make her "noble choice" that way. The way the episode presented itself, you really think she just wanted to watch the big cgi explosion and wouldn't get to do that if they were sent home.