1) Wrapped B/day / Xmas Gift..just means you have get a real gift the same size for her b/day/ Xmas / Wedding.
2) Duffle Bag.
3) Leave it by the garage door (or another location) out of sight until she goes out & you can sneak it properly into the house.
4) Give it to Andrew M who will look after it for you & he can hang onto it until you are ready to take it home ..im sure for a small fee.
5) Leave it under your desk. I used to have heaps of kits under my desk at my last work location - used them as a foot rests for a while. You could always build it at work.. You & andrew can sit together & work on a model together..probably give him the hint to teach him to build & possibly even finish a model ha ha