You really shouldn't put a child in the front unless its a last resort, much safer in the back passenger side. If you have to then make sure the airbag is turned off!
My 172 has isofix in the back and the front so if you have it its definitely worth using it, much safer than a seatbelt imo.
When you say baby seat are we talking a carrier like a maxi cosi cabriofix thats rear facing or the next step up seat like the priori xp thats forward facing? If you go for a non isofix seat make sure it fits the eat properly, get it checked before you buy