Really, you need to ride a bike to tell if it is going to suit you properly. I do not know how sturdy the bikes you are referring to are but if you are not sure how much you are going to ride they might be just fine as starter bikes. I would still buy from a bike shop vs. Academy because you can get some first hand guidance and the bikes they sell tend to be more adaptable -- eg. you can put a new seat on if the stock one is uncomfortable (most are), you can get new pedals or whatnot, etc. A $100 bike is not going to be worth anything if its too uncomfortable to ever ride.
As for bike racks, you want something sturdy. I value my vehicle and my bicycle too much to put a flimsy rack on my vehicle to hold my bike, not to mention the disastrous results if a cheapo one failed or fell off while driving (cause an accident, etc.) If you have a new car or one whose paintjob you intend to keep looking nice, you also want a rack that won't move around so much as to cause scratches or dents... a $30 rack is probably not one that will have the kind of fit and protection of a $80 or $150 rack. (Mine was $140 or so, but is a two bike model and highly configurable to work on either a sedan, SUV or minivan.)
I have a small size SUV now and my bike can fit in the back with the seats down, but before that I got a sturdy and not altogether expensive
Saris "Bones" bike rack for my sedan -- the rack also fits my new SUV, by the way, if I want to use it.
Think about long term value, not just immediate purchase price.