since you already bought the big trash cans, my approach would be to siphon into them, and then use a smaller, liftable bucket to scoop back into the tank. sure, it'll require work but it'll be faster than waiting on a pump.
but if you're bent on getting a pump, it's not such a bad thing to have on hand. not at all necessary for this situation though. my Home Depot here in Chicago is overstocked with small pumps now after the flood we got. Guy there says there's been such a rush on that stuff, as well as shop vacs, he hasn't seen anything like it in his 17 years working there.
if you hadn't already bought the 35 gallon cans, I would have suggested many 5 gal buckets. At least you can move them around. You aren't going to be moving those 35 gallon cans anywhere while you try to swap out the stand.
crazy luck with those beetles, though! hope it all works out.