So first off, we know for certain from the dialogue that the Guardians did NOT know about this arrangement...
1.10 The Last Ceremony Transcript:
GUARDIAN 1: What are you doing here?
NICK: I was just, uh Just checking the Commander's house. Making sure
it's clear. Everything looks good. Just gonna lock up the house right
GUARDIAN 1: You're lying. No one's supposed to be here. Shit! Come on!
Get him in the car! Get his keys!
GUARDIAN 2: You got him?
GUARDIAN !: Follow me.
It's true we know Fred somehow arranged for this meeting to take place, but in truth we do not know how he arranged it. If Hannah's adoptive father was directly involved or not?
But let's presume so. Just because these two men have an arrangement, doesn't mean that they don't have to be careful...
1.08 Jezebells Transcript:
JUNE: But just one thing. What is this all for? FRED WATERFORD:
Tonight, I'm taking you out.- Shall we? - (FOOTSTEPS RECEDING) You
have her pass, too? Yes, sir. Mrs.Waterford went to visit her mother.
She won't be back until tomorrow.
JUNE: Where are we going?
FRED WATERFORD: You don't want me to spoil the surprise, do you? (DOOR
SHUTS) All along there, you can see the improvements we've made. We
took down the tenements, put up a park. The whole grid's solar now.
In previous episodes, Fred has used his power of Commander to sneak June out for a night on the town at private or secret gentlemens' club for Commanders. Even though some of their wives know, it still is a conceit to some of Gilead's lower classes, but more so to the rest of the world, as this practice goes strictly against their religious beliefs, which currently co-insides with Gilead's laws. These things can not become "public"! If they are, there will be consequences even towards Commanders and their families, as Fred's rank was contested in the episode he was in the hospital and June and Serena had to do Fred's work in his absence, which is also against Gilead's laws. We know that despite the white male patriarchy of the this authoritarian society, men still have to watch out for other men.
2.10 The Last Ceremony Transcript:
JUNE: I need you to go now, okay? I need you to be brave, okay, baby?
So, what you're gonna do, is you're gonna take your Martha's hand.
You're gonna get in the car. And you're gonna go home.
It's possible then that Hannah's mother did or did not know either, but she would be subject to consequence, should something go wrong. Neither one of them are with Hannah as she accompanied by their "Martha" and a driver. "Marthas" and drivers probably make for easy scapegoats, but again this shows a precaution towards public scrutiny. Of course it's also possible that neither one of Hanna's new parents knew either. Oddly the house is their house, but clearly not their only place of residence, as some furnishings are covered and June tells Hanna that she needs to go home, because time is of the essence, as the driver interrupted June earlier to tel them they need to leave...
We also know this is a really big risk on Fred's part, because June already tried to runaway once, which is exactly what his wife shouts at him about in the following episode, when June doesn't come home and they presume she ran away again. Serena & Fred argue about the dire need to find her, because of what could happen to them should someone find out!
2.11 Holly Transcript:
SERENA: I'm not leaving here without my baby.
FRED:We shouldn't be here. Someone might've seen our car. I'll make
(and a bit later...)
FRED: How could you be so stupid? They hate you! She's always hated
you! She keeps running away from you!
SERENA: Me? If you'd shown that girl one ounce of kindness, she would
never have left! Kindness? You raped her yesterday!
FRED: That was your idea! I did this to fix your mess!
SERENA: You sent her out here with the father of her baby to see her
daughter? What did you think was going to happen? That she was going
to go home and thank you? You are such a fucking idiot!
FRED: Fuck! When did you become such a bitch?
SERENA: What are we going to do? We can't explain this away. We can't even report it. To have a pregnant Handmaid run away once is bad
enough! But twice! They'll say we're part of the Resistance! FRED:
I'll handle it. SERENA: You'll handle it.Just like you handled this?
They'll put us on the Wall! FRED: Yeah? Maybe they'll hang us side by
At the end of the day it becomes clear that both Fred and Serena, despite their position have to worry about following the rules too and only have so much power. As mentioned in 1.11 Holly, they could be seen as "resistance" simply because June kept running away and because Fred made some kind of arrangement that may have enabled her to do so.