Here is how it went with my group of characters so far...
I have a group of good aligned characters that required no convincing to head off and save the world. They would have done it for free because it's the right thing to do. They still accepted the money though.
The group makeup is as follows:
Human Champion Sword and Board Fighter
Wood Elf Thief Rogue
Human Light Cleric
Human Abjurer Wizard
Wood Elf Beast Master Ranger
My wizard did not have a means of teleportation available (he has Plane Shift though!

), so they availed themselves of Myrkyn's teleport focus. They went in with weapons ready, but no spells other than the wizard's mage armor up. Once there the cleric thought that maybe she should have scryed ahead first (she has the spell ready), but too late now. With the battle cry of the frost giants making their intentions pretty clear, and the fact that no one spoke Giantish, and the fact that frost giants and winter wolves are evil, my adventurers did not hesitate, they attacked back.
The fighter went first (remarkable athlete and 14 Dex gives him a +5 Initiative) and attacked the wolf next to him. He did 39 damage, but failed to knock the wolf prone with his shield (Shield Master feat).
The giants went next. Based on the map that Flamestrike provided I swapped my characters in for their counterparts. I determined that they would attack the fighter (AC 20) and rogue (AC 19) as the closest targets. The cleric used her Flare of Warding to impose disadvantage (4 uses left now) on the big giant's first attack, which caused it to miss, but the second attack hit the fighter for 36 damage. The smaller giant attacked the rogue and hit once for 25 damage, which the rogue reduced to 13 with Uncanny Dodge.
Next the wizard went and used Hypnotic Pattern on the two giants (based on the map he can easily get them in a 30' cube without hitting friends). Despite only a 30% chance of resisting the smaller giant saved, but it did take out the bigger threat.
The rogue used a bonus action to disengage the giant and moved to the opposite side of the wolf that the fighter attacked and managed to finish it off with exactly 36 points of damage (which was a little lucky since it was a couple points more than her average). This also took her off the front line.
The winter wolves went next. Based on the spacing of the characters and the relative small size of a 15' cone they were each only able to get two characters in the area, plus the ranger's wolf in one area. One hit the fighter and rogue, which the fighter blocked with his shield and the rogue evaded, so no damage there. The second was able to get the cleric, the ranger and the ranger's wolf (since none were able to move out of the way yet). The cleric and ranger saved, but the wolf failed and took 10, 10 and 20 points of damage respectively. The third hit the wizard and fighter for only 10 damage, and both saved so they only took 5. The wizard's Arcane Ward absorbed the damage. (Does he need to make a concentration check if the ward takes the damage?)
The cleric cast Spiritual Weapon, smacked the wolf in front of her, drew her mace of disruption and smacked it again for a total of 17 damage.
Finally the ranger went, she and her wolf attacked the winter wolf on the cleric. The wolf with Pack Tactics easily hit twice for 25 damage, but the winter wolf easily made the two DC11 Str checks to keep from falling prone. The ranger then hit with her rapier for another 12 damage.
And that was the round! Overall my groups ability to use reactions to reduce damage was extremely helpful. Damage was good, but none are optimized for extreme damage output. It really hurt that the wizard didn't take out both giants with Hypnotic Pattern. If he had this battle would basically be over.
Final note on the ranger's companion... I can see it being a major resource sink. It has been discussed before, but I wanted to see it in action. Honestly it's Dex save is the same as a couple other characters, but the problem is
all its saves are that bad.
Round two coming up!