I'd have thought best to book in advance, especially if going in the summer season.
Have a look at rentalcars.com for a comparison of the mainstream rental companies, and also look at the independents: Poppy Cars, binicars, Don Cars, etc.
private airport transfers
Re: private airport transfers
Depends on when you're flying; most car hire companies get fully booked in high season.
You mention you need a booster seat; frankly, at the end of your flight, coping with tired and excited child/ren, you may want to avoid waiting in the desk queues at the airport to complete the arrangements before you pick up your car!
Although most of the online companies appear to offer good prices, more often than not, you find lots of add-on costs (some only revealed when you collect) and these bargain prices escalate dramatically. I doubt you'll get a better deal by waiting until you get there.
There's only 2 of us but we always book in advance, using local hire firms who offer clear pricing policy; there are plenty to chose from and if you look on the site you'll find several recommended by members. They'll meet you at the airport and take you to your car, the formalities will be quicker and you'll be on your way whilst others will still be in the airport.
trevx
You mention you need a booster seat; frankly, at the end of your flight, coping with tired and excited child/ren, you may want to avoid waiting in the desk queues at the airport to complete the arrangements before you pick up your car!
Although most of the online companies appear to offer good prices, more often than not, you find lots of add-on costs (some only revealed when you collect) and these bargain prices escalate dramatically. I doubt you'll get a better deal by waiting until you get there.
There's only 2 of us but we always book in advance, using local hire firms who offer clear pricing policy; there are plenty to chose from and if you look on the site you'll find several recommended by members. They'll meet you at the airport and take you to your car, the formalities will be quicker and you'll be on your way whilst others will still be in the airport.
trevx