Hi C..
I don't get what you mean by "secret allowance". Does that mean your husband and their mom doesn't know? or what? (I am always on and off about allowance in general.)
At 16 and 14, the children are old enough to earn spend money. And to pay them for NORMAL stuff (the 'chores' you listed) that we all are expected to do is not much different than paying them to flush the toilet after they use it. I get your motivation, really! You don't want to pick up after them. I often feel like my kids are rabbits, hopping along, and leaving evidence w/ every step! I try not to take it personally, and instead, give a reminder, and employ consequences. You have several options.
A family meeting could lay the cards on the table. With younger children, I have clearly shown them the expectations on paper. With older kids, like yours, I think a great conversation would start with you asking them their views on "what are normal expectations? Writing it out for all to agree and sign helps with integrity. Another conversation to consider is asking them what do they feel are the cosequences of the "what ifs?"
Look, I don't have it all figured out. I often think that is why God gave me so many, to keep trying. hahaha.
ANother approach would be to simplify. REmove their access to the excess. For example, give each just one towel, plenty for a weekend visit. I am betting after drying off with the wet stinky towel they left on the floor will get old fast.
And most importantly, don't let it drive you nuts. As parents, it's hard to not take it personally. We give so much meaning to things, unnecesarily. Most kids tend to be lazy by nature, and will only do what they have to. (me too!)
I could brain storm forever! I hope this helps. ~Cathy