We'd need a map to really help you with this:

Where are the enemy combatants? You said 2 are in the barn torturing the hostage, where are the other 5?

Where is the tied up farmer?

So here's some ideas based on the limited information:

Use your Alarm and minor illusion to try and draw as many of them away from the barn as possible. You are on a farm, have the two half orcs crawl into two nearby haystacks and lure as many of them in that direction as possible to give them an ambush opportunity. If possible, do this by freeing the farmer and getting them to chase the farmer into the ambush without knowing you are there at all.

If not, then send someone relatively "weak" looking, like the gnome in to free the farmer and let him be seen. Then have him run away, pursued by as many of the bad guys as possible into your ambush by the haystacks.

They outnumber you, so anything you can do to limit the engagement to favor you is good. You need to concentrate your attacks on as small a group of them as possible at a time. Ideally you should get them into a situation where all three fighters and the monk can all attack the same guy, drop him with overwhelming numbers, then move to the next guy.

Have the Druid sneak near the barn. Once you lure as many away as possible, have the druid use Animal Handling skills or any available spells to encourage any horses, cattle or other animals in the barn to attack the ones left behind or at least create havok. Then go in and free the Military Guy in the chaos. You can use alarm to create loud noises to spook the animals if the Druid has no skills/powers to do so.

How far away are neighboring farms. Can you recruit the farmers neighbors who would probably object to the enemy's actions against the farmer?