Ok,
this route is my suggestion! It starts and finishes at Spring Wood picnic centre car park, Whalley. There is a station at Whalley, with trains running from Manchester Victoria via Blackburn (destination Clitheroe).
It is as near as can be exactly 100 miles (161 kms). It has a slightly lumpy beginning, and a less lumpy finish with a really long easy middle section. Here's the profile ...
I've marked the highest point on the route, just 12 miles into the ride. It is at 523 ft. To put that into perspective, the highest point on our recent Waddington rides was at 787 ft. This is about as flat as you'll get without going through the local cities. It is an easier route than the Manchester 100 which many riders think of as flat.
The route takies in the coast roads and promenade from Lytham St Anne's through Blackpool and Cleveleys to Fleetwood. Parts of the central Blackpool promenade are currently closed for restoration work and there are diversions in place so we'd have to find our way through them.
A short ferry trip would get us to Knott End for £2 per rider & bike.
There is a good cyclists' cafe at Scorton at the 73 mile point but obviously we could get something to eat and drink as we rode along the promenade.
That's as good as I can come up with chaps! If you don't fancy it, I'll certainly have a go at it by myself when I'm fit enough to add another 42 miles to Spring Wood and back from Hebden Bridge.
My preference would be for a Saturday as transport is easier (and I'm busy on Sundays

but it would be interesting to see what comes up.
I'm okay for Saturdays or Sundays. Trains are definitely better on Saturdays.
Looking at dates more generally, the CC Ecosse rides have a way of people voting for the days they are availible. Would that be useful in the future to either of you?
I tried the voting system before and ended up doing the ride twice, once on a Saturday, and repeated on a Sunday for those who couldn't make Saturdays! Generally, I'd rather do each ride once!