Will you be planning your route beforehand, or will it all be on an ad hoc basis?
I suspect if you're going to do everything ad-hoc, then you will need an array of maps. I guess the most difficult thing here will be translating a path on the map into a daily rideable distance.
However I have gone touring with a pre-planned route so I can certainly say what worked for me. This was basically spending time on the web beforehand, and on the road using a cycle computer and having a smartphone for backup.
I use a site called BikeRouteToaster to plan routes. I don't know how well-known this site is, and I'm certainly aware of other sites that offer this, but I like this one. You get a Google Maps interface which allows you to create routes. Having created your route you get things like distances and elevation profiles there and then, so you can fit your route to what you want to ride for the day. The end result is a file containing your route - GPX is an standard format which has been around forever, it also export TCX files for newer devices.
Central to my planning was a Garmin 800 (I see there is now a new one out, so you may get a bargain). This is quite a high-end computer so you will pay accordingly. However it contains a GPS and will take in suck in the courses from BikeRouteToaster. The big thing about this is that it has a micro SD card on which you can put maps.
Now, don't get me wrong, the display on this unit can make map-reading quite painful, but in terms of showing your immediate vicinity and indicating which way you should go, it works well. You're not going to get lost.
The maps, unfortunately, have to be in a proprietary format, and this again is reflected in the price. However the good news is that there are various resources on the web which will convert Open Source Maps into the format required by the device. I bought a 16GB card and have pretty much all of Europe on mine, at no cost. I used http://garmin.openstreetmap.nl/ to do this, but there are others I guess.
The good thing about using a computer is battery life - my 800 will quite happily run all day with power to spare, and will recharge via USB. And this is the big win over something like a smartphone, which will drain pretty quickly if you're using its GPS all the time.
Having said that, a smartphone is great to have as a backup. Most of the time it just sat dormant in my pocket, but every now and then I would get it out just to use its GPS/maps. I have an application called Memory Map, which offers high-quality commercial maps (Ordnance Survey in the UK, IGN in France etc.), but again which come at a price. I've been using this app for years and have built up a collection of maps... Alternatively of course you have freebies like Google Maps (although bear in mind it is worth caching maps beforehand since you won't necessarily have a phone signal when you need it).
Having the smartphone was my alternative to carrying paper maps, and a 5" screen may not work for everyone.
Like I say this setup worked for me, but I do think it is dependent on how much you want to prepare your route in advance. I realise that overplanning could potentially spoil this kind of holiday if you're not careful.