I want to book a taxi to the airport ahead of time to make sure we get there. Can anyone recommend a reliable service?
Which town or city are you starting from, and which airport?
From Paris to CDG, call G7 taxi. Their English line is 01 41 27 66 99. They are very reliable, but be at the curb about 5 minutes before the scheduled time. The fare will be 50 euros from the Right Bank or 55 euros from the Left Bank plus 7 euros for reserving in advance. This is four up to 4 passengers and luggage.
G7 also has an App if you like to use: G7 Taxi
Another vote for G7 in Paris.
Recommend you do this the night before.
You can use their website, call or use their app - all in English.
Piling on. We have done this many many times and G7 is super reliable, pleasant and helpful and although I always have a plan B for an important airport run, they have never failed us.