I'm going to a huge regional consignment sale in a few weeks and I'm wondering if I should start looking for convertible car seats. We will need 3 (separate cars for daycare drop off and pick up, and my mom watches LO 3 days a week).

LO is 5 months and petite (25th percentile for weight and height). Her infant seat is good up to 35 lbs and 32 inches.

Should I look now, or wait til she's closer to outgrowing the seat? The next regional sale is in September. If I look now, what older seats would you recommended? I know I'll need to check expiration dates.