Congratulations and good luck! My kids are 8 and 4, and jeez am I glad I'm out of the woods on the infant seats...
For when the kids are older: (30lbs and up)
We have a collection of the OEM Quality, massively overbuilt Recaro "Start" Boosters. They were last produced in about 2003. They are very highly adjustable as your kids grow up.
Believe it or not, they are still available as new old stock/ brand new in box on eBay:
Again: These are boosters that are good for kids 30-80 pounds.
They are super safe for the kids (like a Recaro HANS race seat)...
Fully modular/washable covers for spills, etc.
They look and function exceptionally well.
Features stereo mini-plug input for speakers built into head restraint
You'll be there before you know it.
See related post link below.