Also you think my 4 year old will be able, once he's riding well, to go for like a mile or more? I was thinking he won't be able to keep up. When we're actually trying to get places.
My 4 year old will ride a couple of miles easily, but it takes FOREVER. He rides between 4 - 7 mph. For really short distances (~1 mile), I'm happy to let him ride, but much further and it gets impractical really fast. Also traffic is an issue. He's small & hard to see, so if we have to go through certain parts of town, he really can't be on his own bike.
Wow 3 kids on the bike? Awesome. Was it heavy when you also had 2 in the trailer? We have a big hill by my house that you have to go up to get anywhere.
How did you tow his bike?
Towing a bike (any size) with the Xtracycle is pretty easy. Just pop the front wheel of the bike you want to tow into the bag & strap it in really well. Then tow away. If you want photos, look here:
https://familyride.us/2013/11/15/hauling-two-and-three-bikes/Yup -- 3 kids on the bike. I've done it several times -- before and after I added the electric assist to the bike (more on that below). The kids sit in a line on the deck. It's pretty cute.
The setup with 3 kids on deck and 2 in the trailer is really heavy. I didn't try that until I added the electric assist. I have towed the trailer with just my 2 without the assist, but the 5 kids on the bike has only been attempted with additional power ;-)
I've had the Xtracycle for 3.5 years & added the assist (the bafang that everyone talks about) about 6 months ago. The driver for adding the assist was the hills -- my kids + the bike now weigh more than I do & I was just dying getting up hills. I mean, it was possible but I didn't find it particularly fun arriving at parties looking like I had rolled straight out of the gym. Also, my 4 year old would sit behind me yelling "faster faster" which was like having a sadistic personal trainer. So I decided it was time for the assist. If you plan to haul 3 up a hill regularly & are really trying to replace a car, I would recommend getting an electric assist.
As far as cost -- the cheapest long tail cargo bike with an electric assist that I have ridden and can recommend is the Yuba Spicy Curry (~$4000 ... probably $4500 once you add the accessories you need). Xtracycle also sells an assisted bike off the shelf, but it's even more. It's somewhat cheaper to add the Xtracycle leap + aftermarket assist to an existing bike. But I struggled with the higher deck & flex in the frame from that setup.
For my family the money we've spent on the bike has been well worth it. We sold our second car when we got the bike & we have put thousands of miles on it ... probably between 7-10k miles. So even with the expensive bike + expensive assist, we're ahead financially. But a family that doesn't really use the bike to replace a car... well that won't make any financial sense.