I do similar, the extra benefit of this kinda thing is thatmost of the group can get involved. I as a gm can describe the big bad's safe as radiating enough magic to make the wizards hair on the neck stand up & be palpably felt at a distance if he moves closer while my notes say "bug nasty safe, let players spend a few min figuring it out" only to result in the wizard/rogue/barbarian/druid interact with a bunch of knowledge checks that are ultimately part of the players dismantling the wards by....
- Disabling a divination ward that checks to make sure the other wards are in tact & triggers the patyload if it notces them being mucked with
- you aren't sure how well it's gonna work if at all & there's a ton o power in that safe... yea you aren't sure the spell but your syure it's enough to power a disintegration field.
- corrupting the divination check to make the part looking for a specific arcane marked item to accept a different arcane marked item to be present when the safe is opened
- Your pretty sure it will still go off maybe 50/50
- The druid casts plant growth or something to ground the payload into the foundaton of the basement where the safe is with help from the wizard & rogue to make sure that vine grows into the right spot
- everyone runs far away... The barbarian rages, makes a save, & pulls open the door while holding the marked item as directed
- Boom everyone hears a huge explosion & cloud of dust streaming out of the room
- barbarian sits on pins and needles waiting to hear the outcome while everyone rushes in to help rescue him
- barbarian is a little rattled & gets a description of the explosion with the vine taking the brunt of things but he took... roll dice not too bad damage & is okish
The party spent about 15-20 minutes there