I love to bike but those trailers to pull kids in always stress me out and are way to bulky! Yes, if you have two tiny littles and want to go on a long ride that might be your best option, but I was looking for something easy that I could throw a kid on and let one ride their own bike then let them switch off so they don't get as tired and can take breaks. For how cheap it is, it's definitely well worth its money!
We got this seat off Amazon and I initially ordered the one with the side rails HERE but ended up not liking them so we took them off. The little hip bars looked like a great idea to make sure the kids don't tip or slide but they ended up hitting my knees when I pedaled. The seat is so stable as it is so I suggest getting THIS one instead (plus Amazon Prime so you'll get it faster)! When you're holding onto your handle bars and pedaling your basically hugging your child so there's no way they're going anywhere.
My Dad added a little metal bar for the boys to put their feet up on. It's super handy when their legs are long (Oaks is 4 here) to keep them out of the wheels. Just a few scrap pieces of hose, a U hook and a metal bar we got at Ace Hardware and it works just fine! The link HERE has an option for a foot peg but I'm not sure I'd love that as much since it goes straight down and seems like it would be in the way if you're using this for a bike.
I just ordered another one (they're only $25) to add on my husbands bike so we can take both the boys. It's a pretty fun option for this age and I love that they can look forward and see!