Hmm... I don't think it's necessarily a terrible idea but Seroquel is an interesting and somewhat strange drug that would not be my first choice to do this sort of thing. I guess you're asking because it's all you have available though.
How did you find seroquel as a sleep aid? ie, was it effective? If you were prescribed it alongside Adderall, then you must presumably have some insight into how it affects the sensory issues you mentioned, which I'd hazard a guess are amplified when the effects of Adderall are fading and you're trying to go to sleep, and probably a big part of the reason you had insomnia in the first place.
If you found that it was effective at quieting these sensory issues and it did indeed help you sleep then it probably will be effective in helping you sleep through a few days without Adderall.
Although - when you say you plan to sleep through these days, does this mean you intend to take more than you were actually prescribed? This is not necessarily a terrible idea either, quetiapine appears to have a fairly wide therapeutic range, so assuming you weren't prescribed an insane amount already (like... I dunno... over 300mg or something... actually I just checked this to make sure I didn't tell you something dangerous and it appears that up to 800mg / day is prescribed sometimes, although in no more than 400mg in 2 doses, I think usually XR).
You are fairly light though so I'd think you'd be prescribed something on the lower end of that, I'm going to guess you were prescribed maybe 150-200mg once in the evening. I think if you wanted to take that dose twice a day roughly 12 hours apart for a couple of days, you'd probably be OK. Even if you were prescribed 300mg, the same probably applies. It is possible to overdose on quetiapine, not that easily but just don't go absolutely ham with dosing yourself if you find yourself still uncomfortable taking your normal sleeping dose. If you were prescribed less, like 100mg, you probably can push the dose a little higher if you need to but yknow... just be a bit careful. Also... of course this should always be assumed but I am not a doctor or medical professional of any kind and my advice may not be good advice, I don't really know and I've never actually taken quetiapine, I speak just as someone with an armchair interest in pharmacology and personal experience with a lot of drugs, including amphetamines (or "Adderall", if you like, my own Adderall was just a 3:1 blend of dextro- and levo-amphetamine though, just out of curiosity to see if there really was anything special about that ratio - IMO there wasn't).
So IMO I think it is not explicitly unsafe and not the worst idea for sure although quetiapine is a strange choice as an insomnia prescription for someone already prescribed Adderall, since it's drowsiness-inducing effect is kinda just a messy side-consequence of it's other mechanisms of action, rather than being selectively conducive to quality sleep like so many other options. This would surely only happen in America... regardless though, whether or not it will have the desired effect for you is a bit more unclear since a few days might not be enough to appreciably affect tolerance, especially since you self describe as having a "problem".
If you want to try the cold turkey method regardless though, if after a few days you find that you're really sufferring, perhaps you could take just a lower dose of Adderall, like maybe try to cut right down to 35mg or 40mg, which is on the higher end still perhaps but not as unsustainable as 70mg. And if you just can't bear it still maybe take a little seroquel, perhaps half the dose you'd usually take for sleep also... try this for a few days and see if things improve.
Seroquel and Adderall are prescribed together so there don't appear to be any majorly problematic interactions but I would still personally give yourself a hard cut off at the 7 days point with the quetiapine / seroquel if you find yourself still taking it at that point just because, as I say, it's a weird drug, it shouldn't really be considered a sleeping pill, it's a somewhat atypical antipsychotic with a range of potentially dangerous side effects compared to a REAL sleeping pill - or "hypnotic" - like a solid z-drug which would absolutely work for this plan with comparatively little risk, IMO.
You say also that you have an "old" Seroquel script, does this mean that you no longer have issues with insomnia?
If it's an option, I'd try to get a prescription for a less weird sleeping aid, again a solid z-drug would surely be a good option, zolpidem would certainly deal with your sensory overload issues IMO although it's also most liable to a be a little "too fun" and prone to inducing strange behaviour, like deciding to take your usual dose of amphetamines anyway... eszopiclone would probably be another good option, sleep inducing, not especially compulsive or prone to inducing weirdness, kinda relaxing enough to ease you through some sufferring. Even just zopiclone if you can get it. But if this isn't an option and if you've tolerated Seroquel well in the past then I do not think your plan is a bad one exactly, it might not work as well as you hope but it's probably not actually dangerous. Again though... not a doctor! A better option would be to ask a real doctor.
But maybe not the quack who prescribed you 70mg Adderall and quetiapine for sleep, unless you have some other condition not included in your post.
