O.K. so Charlie is making eye contact in the house - REWARD CLICK/TREAT FOR THAT
He'll start to associate the click/treat/eye contact!
Then work on the lead with Charlie in
your own garden, get him used to click/treat means EYE CONTACT with Mom. Less distractions there and if he's distracted in the garden, then work in the house with him, even less distraction. Use loose lead here.
Try to work with him when you're alone together, even less distractions.
Also, when I first started in the street with Ra Kismet (we worked in the garden first) I would call him (he's always on the lead, that's the law here) say "Hey Ra Kismet/Rakins) didn't always work the first, or even the second time or ......many times after the first few times I tried BUT EVENTUALLY he 'got it'. When he responded, even for a nano-second, click/treat SEVERAL TIMES OVER not just ONE treat but masses of treats! And now he will easily make eye contact with me without being asked. Ra Kismet isn't as old as Charlie and has only had his problem for a short time but it still takes lots of practice/work and TREATS masses of treats, be VERY LIBERAL WITH TREATS before they 'get it' in the street. Everything 'distracted' Ra Kismet, I always say he's a 'nosey parker" as he wants to know what EVERYTHING AND EVERYBODY IS DOING! As you say, there are all those interesting things, smells, people opening doors, people walking down the road, doing their gardening, the list is endless and ALL AT FIRST much more interesting than making 'eye contact' with Mom.
Do you do any heel work with Charlie? If not, start doing that with him IN YOUR OWN HOUSE/GARDEN. He'll definitely have to keep close to you and start making eye contact.
I used a 'lure' food held in my hand and kept my hand down close to my side, when I first started doing 'heel work' with Ra Kismet. He kept his nose firmly on my hand, I kept a firm grip on the treat, FOR A PACE then I allowed him to have the treat - click/treat after ONE pace. Then we progressed to TWO paces and so on until now he'll do heel work and gets his reward after quite a stretch
And he has to maintain eye contact because he doesn't know if I'm going to 'change directions' - take it very S - L - O - W - L - Y at first with change of direction and don't expect too much,
Charlie will 'get it' but you're going to have to use lots of patience and lots of treats with that clicker. You are using a clicker I hope, if not, believe me they're the cheapest and most effective training tool on this planet. Worth more than their weight in gold!