Just go with it (Pretending to not know)

You decide you can live with Ellie sucking your moms cock regularly even if they didn't tell you about it not like you can reveal you know it without exposing you peeking at your mom

"Very well you can use her when you need to"

Your mom stops before leaving the room "Oh! That's great news it would have been expensive to pay for someone" she smiles very wide almost predatory like. Before she turns away you notice she has an erection now and she is massive, the skirt that went to just above her knees is now bunched up and hanging over the top of her cock as it barely blocks half the 12in hard cock and completely exposing her sack.

She doesn't seem to notice that she was exposed must have been because of her condition. She stops at the door of the kitchen and turns around again with everything covered up "Oh take your time today and tomorrow and discuss this I know it's a big deal and all"

Ellie Didn't comment on what she saw either but she says "Oh she is already being affected by it... But don't worry its just some relief between girls and all" she says

"ye- yeah" you stutter a bit, the thought from earlier about what your Girlfriend would look like sucking on your mom's cock come back through your mind this time with her trying to take that foot long monstrosity.

"Ohhh you are excited by that thought? the thought of your Girlfriend and your mom together?" she pats you gently where you sported your own tent, nowhere near as grand as your mom's but still there. she whispers into your ear "her lips on my pussy while trying to hold a conversation with you" The twitch in your tent is your answer

"well let me get you some relief "winking at you, she slides off the chair to under the table and pulls out your dick before putting it into her mouth

you notice something, the same noise from earlier that your mom told you was from the food in the oven was back but this time it was coming from her sucking on you and much more quiet. probably because you don't have the size your mom has

the entire time you were setting the table she was sucking on your mom's massive dick, you remember how she moved forward when you approached either to hide what was happening or to prevent Ellie from stopping, you don't know but you do remember that she didn't stop, and that your mom was bouncing her tits at you which you disregarded as normal. but now you know she was thrusting into Ellie's throat.

between your imagination and her decidedly skillful actions you warn her you're close and she pulls back and lets you cum over her face

in the afterglow you realize your mom will probably be teasing you more

Ellie wipes her face "I'm going home tonight we will discuss this tomorrow after everything has calmed down"