In these games you have option to choose sleep with mom in her bed whenever you want:
Straitened Times - in this game MC live in motel with his mom and two sisters and they have a total of 2 rooms and you decide who you want to share the room with and whether you want separate beds or just one bed, so you have the option of choosing a room with your mom with one bed and then you sleep together every night and you have the option to change rooms every day at the family dinner
The Twist - MC can set mom room and her bed as default to sleep in, of course this option is only available when you have reached a certain level of affection with mom.
Dark Magic - MC can sleep with his mom in her bed whenever he wants, of course this option is only available when you have reached a certain level of corruption of mom.
Summertime Saga - MC can sleep with his mom in her bed whenever he wants after having reached a certain level in their relationship
Insexual Awakening - MC can sleep with his mom in her bed whenever he wants after having reached a certain level in their relationship
Become Someone - this is game where dev used real porn and not 3dcg or 2dcg graphics but if you don't mind such games them here you also can sleep with mom in her bed whenever you want, of course this option is only available when you have reached a certain level of affection and corruption with mom.
Son Of A Bitch - qsp game using also real porn and the same possibility as in the game Become Someone
In these games you have sometimes scenes when you sleep with mom in her bed but unfortunately you don't have the possibility to do it every night like in the other games which I mentioned above:
Away From Home - MC sometimes can sleep with his mom in her bed.
BangCity - MC sometimes can sleep with his mom in her bed.
This Is Not Heaven - MC sometimes can sleep with his mom in her bed.