So, you want to lead a ride..
In which case, you will need a route. Thankfully, this site makes it really simple to find one.
Step 1: Check the wind direction
The unwritten rule is 'tail wind on the return leg', so you need to look at the weather forecast for the day of the ride and see which way the wind is blowing..
E.g. In this example, the wind is blowing towards the East / North East, so ideally, you want a route which heads out West / South West.
Source: BBC Weather
NB If the wind speed is below 6 mph, it probably doesn't really matter and just pick a cafe you've not visited for a while.
Step 2: Pick a cafe
In our example, we're looking for a cafe SW / W of Cambridge. Look at the list of cafes on this site to see what options you have e.g. in our example below, all the cafes circled would have a tail wind on the return leg to Cambridge.
Source: ELSR cafe list
Read the cafe details on this site and pick a cafe which is suitable for the size of group and the anticipated weather. Some cafes have limited indoor seating or no heating, so aren't very suitable for cold or wet rides.
Step 3: Pick a route
Once you've picked a cafe, go to the cafe page and look at the available routes which pass by that cafe.
When deciding on a route, check the length is suitable for your group and that the target cafe is roughly halfway round the route (or a bit over eg 60km along a 100km route).
Step 4: You're all set
Download the GPX file from this site and upload to your bike computer and away you go: GPX Download Guide.