Honestly, I'd recommend having a heart to heart with your mom. Ask for a bottom shelf or the door of the freezer, offer to place them in a box or a rubbermaid container...last resort, buying a tiny fridge ($50, maybe?) will be worth the extra $$ because you'll be saving it by buying frozen instead of live. On the flip side, some mothers can't eat dinner without thinking of dead animals in their freezer. If this is your mother, this is how I kill rats (when I can't get them f/t): get two pillowcases that you don't particularly want anymore. Double them (one inside the other). The second bag is for blood cover, sometimes they bleed...dont want that all over the place. Either hold VERY firmly or form a seal at the open end (tie it, rubber band it, whatever...) find a nice, flat surface (oh, Mom's counter would be great for this
) and insert rat. What you'll do is bring the pillowcase over your head and right down onto the counter...very quickly...as hard as you can. They will almost always have nose bleeds...so watch out. At this point, if you are faint hearted...you might wanna drop the pillowcases and leave for about 2 minutes. If you have not hit hard enough, they'll have seizures and die (if you're lucky, otherwise you get to try again). If you have, they should be dead already.
I never suggest this to anyone...and found this out purely by accident. I will never do it again, but I know that it is a sure way to kill rats. I live in a hot state, heat stroke is a horrible way to die but if you accidently put a rat in a small box and in the sun. 10 minutes flat.