My two kitten's are also 16 weeks. I take mine out on a lead, started using Dukes but it was too heavy I took the weight but I had to be very careful.

We had a bit of a panic, because our dog can open doors that open inwards, he hits the handle and pushes his weight forward. Hubby had closed the room door to contain the kittens while he let Duke out to toilet. Meanwhile the phone rang while he was pre-occupied on the phone Duke came charging in opened the room door and both kittens had access to the garden fortunately only one ventured out and froze so it was easy to bring him back in.

I am getting a large outdoor cat enclosure soon, so that will make life easier especially on days like today.

Sue