My kids always fall asleep on the bike and having the recline feature has been great for that. They are almost 3 years old before they stop sleeping on the bike rides. I think that the movement of the bike just lulls them to sleep.
At 5 months old, you are going to need that recline feature, although most are going to say no biking until 1 year old, because their necks aren't strong enough to support the weight of their head and a helmet. If you are going to give it a shot at 5 months, definitely only do it with the seat reclined.