You rule out sleeping with your Mom in her bed, as while it had the advantage of being close to her in case of emergency, it was possible she could roll over in her sleep and crush you.
Sleeping anywhere near your mother's face was just asking for her to accidentally swallow you in her sleep, when her subconscious instincts are in control rather than her conscious mind.
On the other hand, while it would probably be very safe to sleep in-between your Mom's huge ass-cheeks, you didn't really want to spend all night being woken up whenever she passed gas, let alone breathing it in.
Blushing, you ask your mother to sleep between her sizeable breasts, because it would not only keep you warm and safe through the night, but it also keeps you close to her in case you need any help.
Your mother seems to beam at your choice. "Aww don't worry sweetie~, Mommy's soft boobs will keep you nice and safe all night!" Her voice was full of maternal affection, but you swore you heard something a sultry undertone.
Your Mom changes into her negligee nightwear right in front of you, your shrunken size seeming to have caused her concern for you to override any sense of modesty, especially when she told you to undress too, under 'threat' of her undressing you herself. "Those clothes have been rolling around on the dusty floor before you woke up sweetie, you'll get sick wearing them." The fact you had no other clothes that fit you at this size didn't seem to phase her.
Soon, your mother climbs into bed, cradling you in her hand as she manoeuvres herself under the covers, before she brought you to her chest, free hand pulling her breasts apart, and gently tilted her hand so you would slide right down her cleavage. As soon as you were between her boobs, you Mom released her tit, letting the two soft mounds pin you between them. "Goodnight sweetie~" Your Mother gently whispered, her voice slightly muffled to you but still easily understandable, before the constant sound of your Mom's heartbeat began to lull you to sleep.