Family Ties/You could try your luck with mommy.
I am almost sure she said I want a lot more. You think yourself before you turn around and walk back over to your mom. Through the window you can see your dad still puttering around outside the R.V. organizing everything for the trip. You climb onto your mom's lap facing her and slip your arms around her neck. With out any prompting from you, you feel her arms encase your small body. "I would rather be right here with you.." You whisper, your mother's tits pressed against your smooth chest with only her robe separating the two of you.
"Oh Timmy.., I..," Before she can further her statement you risk it all and press your lips against hers, injecting your tongue to her mouth. Your mom fights for all of two seconds before she tightens her grip on you and pulls you tight, driving her tongue into your mouth with lust equal to yours. Once your sure all her resistance is gone you pull your arms from her neck and grab ahold of her robe and yank it open, exposing her huge tits to your horny eyes,. You break the kiss and slump down on her lap and heave one of her breasts with both of your hands, pointing the hardened nipple towards you mouth. "You have the biggest fucking tits mommy." You whisper before driving the sensitive nub into your mouth and start to suck.
Your mom moans louding as she grabs the back of your head, pulling you deeper into her boob. "Fuck baby..., I can't believe you banged your sister last night." You had a feeling that was the case considering the way she treated Heather just before. "I wanted to be the one to pop your cherry.., but your horny sister beat me to it." She moans as you pull her wet nipple out of you mouth.
You take ahold of her hand and slip it between you and press it directly against your throbbing boner, which your moms starts to squeeze and pump gently. "So now I have had some practice for when I fuck you." You assure her, right before taking the nipple from her other breast into your mouth, giving it the same treatment as the first.
"God damnit Timmy..., you make me so fucking horny. You have no idea how long I have been waiting for this, how many times I fucked a vibrator wishing it was your cock." She admits, her hand starting to pump your cock with more need now. "Shit, if we don't this right now your father is going to walk in on me fucking our son." Despite her words she is restraining your head against her tit, unwilling to let you turn her nipple loose from your powerful latch. Eventually she pushes you away, forcing you to sit up on her lap, it doesn't stop you from grabbing both breasts in each hand and massaging her mounds. "Oh god baby stop!" She begs. "Go up stairs and tell your sister that you and her are going to the back bedroom of the R.V..., I'll join you as soon as I can be sure we won't be disturbed. Then you can spend the 6 hours to the lake fucking the hell out of us both." She coos, her hand still pumping your cock through your boxers, your hands still groping her titties.
As turned on as your mother is right now it wouldn't take much to get her to fuck you. You could.
On the other hand, your dad could walk in any second and though your unsure what his reaction would be, you are sure it won;t be good for either of you.