Traveling while tall & with a baby

I’ve found tips for either or but not for both. I’m 5’10” & my husband is 6’3”. We usually sit in the exit row because of how long our legs are. But this time, we’re flying with our 5 month old for the first time. Any tips on where to sit on the plane? Should we get an extra seat for baby? I’m going back & forth between the Go Comfy option on Spirit airlines where they block the middle seat or getting the Main Cabin Plus on AA but that would mean holding baby the whole trip. Anyone have any tips or suggestions?