Nice descriptions and I agree those gates are boogers, but doable even with the tandem. You are also correct about being able to go from the Pere Marquette picnic area to the lodge and park welcome center. It's not much further and all on paved trail.

They've just ended for this year, but during the summer Trailnet has the Tuesday night riverfront rides. Free (unless you park in the garage for a dollar) and supported. We go up to the poor firetruck on the chain of rocks bridge and back. Paved trail.

We also ride the trail around Creve Coeur lake, over to the Katy trail, up to St. Charles or the other way to as far as we want to go, and back. The Creve Coeur side is busy. Paved until you reach Katy, then crushed limestone which can be very dusty.

Grant's trail starts in Oakland (near Kirkwood) on Holmes ave and goes to Orlando Gardens (55/Union area) and back. There are several trailheads along the path. There's a side trail that takes you up a hill to a short loop in Clydesdale park, another short side trail that takes you along a creek, a bmx area near Orlando Gardens and Grant's farm is also accessible and has a bike rack (weekends only). This trail is busy. Paved.

Trailnet.org has maps of area trails. Also check out the MCT trails in Illinois. Great paved trails, most sections not too busy.