I’d personally do a fairly quick ride for the first one to waken everything up and then plenty of stretching all week, with zone two on the other two rides.
Even if you pootle at 22kph on the 3hr ride, you’ll inevitably do 2/3rds distance easily so the 100km should come pretty easily.
Biggest risk will be getting swept along early on with a group that’s too quick – you can think you’re fine but really you’re working too hard. If you are in a group, and you feel like you could drop them all without killing yourself, you’re probably doing alright. If you’re comfortable but getting to the front for a turn is an effort, you’re probably in too strong a group. If you’re falling off the back on rises and working back to them on the flat/descents, it’s way too quick.
That’s a very cautious approach but it will see you round. Or you know, MTFU and go balls out from the off, no guts no glory eh?