Like if I have 5 eggs and 1 LV.100 Emboar, would it take longer for the eggs to hatch since they are not surrounded by strong Pokemon?
No, each Pokemon that the egg will hatch into takes more time. If you have a Pokemon such as Chandelure with Flame Body in your party, it halves the time. So no.
See here for the amount of steps (Scroll down):http://www.arkeis.com/breeding.htm
All eggs take a certain amount of steps for example (this is made up this one) 6587 for Tepic egg
It doesn't have anything to do with your party but if you have a Pokemon such as magmotar with the ability flame body it takes less steps hope this helps