Whatever you buy, install them correctly! I'd suggest you call the local FD and stop by and let them check the install before streapping a kid into it. Doing accident reconstruction, the only severe injuries to kids were when the car seat was not properly installed. If you think it is tight, it should be tighter.

I did an accident where a mom and a teen were killed (front seat) and the toddler (in the back seat) was basically unharmed due to a 40ish mph rear end impact. Car seat saved the toddler.