Yes, booking the flight with a passport that is about to expire or even with an expired one for that matter is not an issue. The important thing is that you must renew your passports before you travel on them. A passport is not valid with less than 6 months left on the expiration date, so it must be renewed prior to your travel.You can apply to renew your passport in advance of expiry and up to 9 months validity remaining from your old passport will be transferred to your new passport so you don't lose out.