E.J.
I went a whole summer without a car. I biked everywhere including the grocery store. I had a bike trailer that was a Schwinn. It had a connection to the bike and also a safety strap, so there was a back up method to hold him on there. I bought a 2 seat trailer despite only having one kid, so I had room for cargo. I loved it. I stayed in shape, I spent less money on groceries and only bought what I needed. The store is only a mile away so I could bike home with my meat fast enough. I have never in the 3 years I've been pulling him had him go rolling down a hill and I've never feared his safety in it.
I'd say that if you are that energetic to go for the bikes!!! My son is now 6 and while he can bike his own on very long bike rides I still put him in the trailer. (He's small only 40 lbs) I think it's awesome that you are considering it! A bike trailer may be around $100 but you exceed that easily in gas, insurance, plates, etc. Best of luck to you!!!