I took my DS out from 5 months old... this was in a trailer though.
I picked a trailer over a seat as I thought it’d be better for long rides as it’d be more comfortable, protect him from the weather better and mean he could play with toys and have drinks and snacks to hand. I thought it’d also be better for transporting a picnic and balance bike.
My DS is now 2.5 and he’s been going out for at least one trailer ride a week since he was 5 months old. An average ride is about 30 miles over 3 hours (it’s hilly here hence the slow average speed).
I’ve even towed him up Mt Ventoux (which was actually much easier than the climbs I’m used to in Derbyshire).
Yeah so as you can guess I’m a very keen cyclist! Luckily my DS absolutely adores his trailer rides. We take a picnic and his balance bike and make a day of it.
I have a Burley Solo. It was the only bit of baby/ child equipment I took any interest in and it’s been worth every penny. I spent ages researching. It’s light weight. It packs fairly small. It packs/ assembles quickly. It handles incredibly well - I’ve actually done quite a few mountains with it and it’s been really stable descending/ cornering.
So I got the ‘baby snuggler’ which Burley sell separately which I used until about 14 months. It cradled my DS in the seat.
I tow with my winter road bike. Because it’s hilly I have a crazy cassette (11-32 - I had a road link fitted so the rear mech could cope) which means I can happily tow up 15/20% gradients. I wouldn’t have any issues towing with my best bike (full carbon all out race bike), I just chose not to.
I ride a mix of trails and quiet roads.
Having the trailer has saved my sanity and done wonders for my fitness (my FTP is better now than it ever was when I raced!!). It’s also a really lovely way to spend the day with my DS, we chat away whilst I’m towing, then have a lovely picnic somewhere pretty.
I hope this helps!