car seat

so my son is now 15 months and he only used his infant car seat for about 8 months before we bought him a convertible one. that being said his sister will be here on August 25 or a lil before. we still have his infant car seat but then I look it and i feel like it's not enough head support for babygirl. like the head piece that it came with feel so flimsy and its graco..I've been looking at the babytrend car seats and they look more comfy for baby's head..what do yall recommend I do. I need to decide because time is cutting too close lol