Agree with a rear-carrying rack, once you're used to it, they only take minutes to put on. Roof carriers create quite a lot of drag when loaded up, and it's so easy to forget about them when you drive under a height-restriction barrier!
Do make sure your number-plate and lights are all visible once loaded, and you may find your rear-view will be restricted.
We have both - for one bike, the carrier stays on top of the car all the time, but we have a Thule tow bar one for all our bikes. It takes 5-10 minutes to put that on and is easy to do, and much easier to put the bikes on.
Takes about 10 minutes to fit the back of the car rack, then another 10 or so to get the bikes on.
You do have to get it good and secure, if they bounce at all you end up damaging the paint (lesson learned the hard way0. While ours was supposed to fit three it was quite an effort to get the 3rd on on there, usually we ended up with two on the rack and the kids ones in the boot.
Roof rack is quite easy to fit on the car providing you can leave the bike mounts attached to the roof bars. Since we didn't have space to store it set up we had to reassemble it each time. We sold it as it was too much faff.
Now have a towbar mounted rack which is great. Fits in a couple of minutes and we can fit all 4 bikes on easily.
We have a Saris Bones. Can fit it and the bikes in about 15 mins. There is no way I would stand a chance of getting bikes up on the roof of a car. However you can't get into the boot on a long journey without taking the whole thing off - we got stopped at Calais and they wanted to see what was in our boot. Luckily they could have a rummage over our back seats but we saw other cars having to take off rear mounted bike racks.
I'm thinking of getting a rear mounted carrier for my Golf - haven't really looked into it yet as only considered the roof ones initially. Am I right in thinking you can't use the boot whilst the carrier is on? So if stopping at a service station, you need to take bikes off before getting picnic out of the boot?
Inside the car for the bikes, get a roof box for stuff if you need extra space. Securing them to not fall off is a pain, people forget about height barriers, it kills your fuel economy, and they can be easily stolen if you leave the car anywhere.
But of course you need enough of a car that you can fit 3 bikes inside, but as there are only 3 of you, split folded seats and you're away!