Advantage is very expensive, but all of it comes out of my emergency fund. I swear, even saving $5 a week will grow quickly to help you cover situation such as this. Each tube is 1 application for 5 lbs, so if your kits are 1-2 lbs you would only need a drop of the solution to treat each kit. 20 kits @ 1lbs each, you would only need 4 tubes, maybe 5 to treat all the kits. Where it will get expensive is your adults.
20 kits @ 1 lb each = 4-5 tubes
12 adults @ ? = ?
If your buns all weigh under 5 lbs, I can try to figure out how much advantage you actually need. You can also buy the bigger tubes made for larger cats if the adults are over 5 lbs. The have different dosages. If they are leaving in 3 weeks, you would only need to purchase a few.
Cat Weight Advantage II Availability
Under 5 lbs. Kitten 4-packs only
5-9 lbs. Small Cat 4-packs & 6-packs
Over 9 lbs. Large Cat 4-packs & 6-packs