Once I worked out that we could hire bikes (why do no hire car services provide bike racks?), I quickly booked the only accommodation that I could find, and waited for October.
The weather did not live up to our expectations, but everything else did. Nick and Ross at Aberfoyle Bike Hire sorted us out perfectly. They were super helpful (especially when this summer another rural bike shop wasn't even picking up the phone). The cottage we hired was very nice and perfectly located - a max 5 minute walk from 2 pubs, a big co-op, and a tonne of cafes, and plumb on the bike routes. It is so nice to be able to get newspapers while on holiday, to know there's a chemists near by, not to have to worry if you've forgotten something (all challenges we've encountered on other ventures out of Edinburgh). Also excellent wifi and mobile connectivity.
Despite the rain, we had a blast cycling around the 'Gravelfoyle' routes. The surfaces are all different, but excellent. The gravel roads are mostly vehicle free, and the few utility vehicles we saw were all very cautious and friendly. And we only covered a fraction of the possible routes.
We did a short loop around Lochan Spling to test our bikes the night we arrived. Then a long but fairly flat loop around Loch Ard, and paths south of it, checking out Black Linn of Blair Vaich, and various historic ruins. On our one (mostly) dry day, we did a big, hillier loop in the Achray Forest, on NCN 7, coming back via Duke's Pass, which dropped us straight back at our front door. Both of these were more properly half-day rides, but we stopped a lot to take pictures, explore, and eat. My one complaint was that the 'waymarked routes' on the Gravelfoyle website didn't entirely map onto the waymarking on the ground. At any rate, they have different names to what is used on the maps available in the super friendly tourism office, just next to the big (free!) car park. We found it helpful to have OS maps and a GPS to show us where we were. There are also tonnes of routes online, using Komoot.
The start of the paths where NCN 7 leaves the A821 are also worth exploring on foot - lots of stuff for kids to play on, waterfalls, art, and a hide where you can watch red squirrels and birds.
So, yes. Do go to Aberfoyle. It's beautiful and friendly and well worth a visit.