Recently moved to TX and there's a state park near our home with hilly terrain. I'd like to ride around with my toddler. What carrier + bike combo would make the most sense? I have a commuter bike but I'm open to a mountain bike or something similar that's better suited.
You don't need a specific bike to ride with your kids and have fun. Very likely the commuter bike you have will be perfect, and if you need a MTB then the trail will be too much for the kids.
I would explore two options.
- The "over the top tube" kiddy seats where the child rides between your knees. These can fit to most bikes using a main spar. Both riders can talk and be heard, and the child doesn't have their forward-view obscured. Child can even have a nap on the padded dashboard. This also keeps the added weight central. Downsides, there's a big plastic seat between the rider's knees. They're not cheap, and there are weight/size limits which your child will reach quickly. And the child can't help with pedalling.
If you have more kids coming along in the future, then a short usage window for this child may not be a big issue.
- Tag-a-long style adapters to connect a kid's bike to yours and make it a towed trailer. These let the child ride their own bike but get a help from you. Advantage is the child can go as far as they can then get hooked up for the rest of the ride. The tow arms can take up to 20" wheels (needs confirming) so you can ride with a larger/older kid. And the kid can coast or pedal as they see fit ("Help Mummy get up this hill! PEDAL!!" )
Downside, child is behind you and hard to see, however once secured you've got no risk of leaving them behind. You also override their balance mostly, but a determined kid can make the adult wobble.
There are versions that combine the kids bike with the hitch, but these cannot be ridden separately, and the goal is to get the child riding and tiring themselves out !
Finally you're American. My impression is that for Texans, bicycles are destination-activities, not transport to the activity. So consider how you're going to move your bike and the attachments to the state bike park. Personally, I'd ride but I'm not familiar with your roads, or your confidence level to ride on roads with child.
I suggest looking at a top-tube saddle of the type sold by MacRide or Kids Ride Shotgun. This saddle type is distinct from the top-tube seats in @Criggie’s answer, and a much better bet for older toddlers, especially in hilly terrain.
You don’t have the bulky seat-surround from the full bucket seat, and the kid gets to learn about how to move their body with the bike.
This setup lets you get to more varied terrain than either the seat or the tagalong trailer (which does not allow off-road usage.
A dropper post (telescoping seatpost like in an office chair, typically with the release lever on the handlebars, comes stock on mountain bikes in the price range you mention) makes these even better, as you can lower the seat to comfortably stand over it when stopped and then raise it up while moving to get full leg efficiency.
I also run swept-back mountain bike bars to get a bit more room around my kid.