I admit to being a novice and having killed a good number of orchids in the last year - all from ignorance. First bit of advice is to keep reading on here and orchid information provided by the American Orchid Society.
AOS | Home In the short time I've been on this board I have learned more about taking care of orchids than any other website I've found and the best part is the people on here, they don't make you feel like an idiot or laugh at asking the most basic question or stupid question (like me thinking a dying Dendrobium was suddenly coming to life when in fact I had a mushrooms growing!!!
While I could be wrong, I've never heard of using Miracle Grow on orchids, while I don't know if it would hurt them, but I would go to a local gardening center and pick up a fertilizer specifically made for orchids.
There are tons of posts on this board with different fertilizers that people swear by. You may want to ask your Mom if she ran across any fertilizer etc when retrieving the orchids from your relative to see what they are used too.
Most orchids do not like being in standing water (I learned this the hard way) and need growing medium that allows for good drainage and air circulation. Phals for example like to drain well and dry out prior to watering, epidendrum being a Cattylea like being a bit moist and not drying out as much. (someone correct me if I'm wrong on those two points)
If you get a chance, take a pic of the plants and post them on here. With all the help available on this site someone will give you more specific information based on the type of orchids you were given. You can always use the search function on this board to find informataion specific to your orchids.
btw, welcome to the world of orchids, be forewarned, these plants are more addictive then crack!!!