Hey, Reindeers are not native to south east asia unless you bring one from a cold country. People can do anything these day. I have people petting Huskies here. Anything is possib;e.
If you really wana visit meghalaya than i would suggest to go beyond shillong to places like cherrapunjee , jowai , dawki , etc cause that's where you will see the amazing beauty of north-east
Try Taj Jim Corbett national park.
It is awsome and cheap comparing other taj group hotels resorts.
Also Club mahindra having a pretty resort at the same place.
Check it whichever is suitable to your budget.
4 Day is a lot of time... Start from the top Narkanda, then kufri, Shimla, solan. If you are going Chail don't forget the resort in water.. Its amazing, Also, Chail is another route and not in one line.