Princess Purr, I just don't have the experience to know if that will work for Snowwhite. I've PMd a breeder who I hope will find the time to check in here and provide you with some advice!
As to the rest, I'm sending you a PM. I'd really like to help you locate resources to help with your ferals! I don't recall whether Ashton and Sherbert are males or not, but I'm afraid that if you wait as long as you plan, you may have more kittens on your hands...
...and the only other thing I BEG of you is to NOT take the kittens to anything other than a no-kill shelter! Around here, that wasn't an option, because the no-kill shelters have long wait lists. We called in October and November, and we still haven't been contacted by one. So please start looking today, if you plan to take them to a shelter instead of adopting them out. If you live in an area with a wait-list, you might need to make those arrangements now. But I want to make it clear - we did not take the kittens to a "kill" shelter. We took care of them as ferals outside while trying to find them homes. We were faced with a total of 8 surviving kittens from two litters, one turned up in July and the other was in August. We just got word that there's someone interested in adopting the last one without a home... so it takes a lot of work and patience, but it can be done! They all survived the Winter, anyway.
...so I'm not sure what advice to give you about this, but kittens really need to be with their mums for 12 weeks.
Anyone should please feel free to post different thoughts or advice but....
They way we handled pregnant females here was to let her make the nest outside - that way the little kittens will learn how to live on their own from mum. Then at 12 weeks, we trapped mum and took her in to get spayed - all the while, we provided food to the kittens (and mum) and spent as much time as possible with them outside (slowly) so they got socialized. This way you can keep the kittens around as long as they need to be with mum, get her spayed yet let the kittens have the time with her they need... and work at finding them homes (via posters, word of mouth, etc.). Now - if you haven't found them homes by the time they're six weeks, then if they're not inside, dh won't make you get rid of them. They can have the time they need with mum and you can get Lilly spayed sooner (and not being a nursing mum, she's far more likely to go into heat).
If the kittens are still with you by the time their adult teeth start to come in (that's when it's time to get them spayed and neutered!) - which happens somewhere between 4 and 6 months - then you can get the kittens spayed and neutered too. It can be expensive (along with the shots), which is why I'm PMing you. I'd like to see if I can find low-cost or free spay/neuter resources for you.