OP, what your solicitor is suggesting is a kind of “standard” template for shared custody but in your case it’s different as 1. there are concerns about his drinking and being in charge of the kids 2. He sounds like he isn’t actually pushing for overnight contact or 50/50 right now at all and it sounds like the kids could very much do with stability right now - please don’t feel that by suggesting the kids generally live with you and he spends time with them, you’re alienating him, it’s totally fine to have one parent with primary “custody” and the other free to see them regularly if that works for everyone 3. Both of you actually hope to reconcile ideally and he doesn’t have his own place.
What works for both parents and the kids can look hugely different in different households. And as long as everyone feels it works for them that’s fine however non standard the solution is. Plus it can change over time depending on various factors.
So think about first your children’s safety and wellbeing (this is what family court would consider if and when it ever needed to go there). I am worried you may still be slightly in denial about how safe they are with him if he has been drunk in charge of them before. If that’s the case I’m not sure his taking them out to soft play etc is a great plan? Or does he only tend to drink at home? From what you’ve said so far, it would not be unreasonable to insist that in the short to medium term, either you or his parents or someone else you trust is with him when they are with him too until he has been completely abstinent for a long period of time (like months).
I agree in the long run (I know you’re hoping there won’t be a long run but who knows right? Best to start as you mean to go on if you are not able to reconcile), it’s going to be easier on the kids and also you to avoid blurring boundaries and not have him care for them at your home.
If and when he knocks the alcohol on the head you can look at the whole thing again and might come to a different arrangement while you are still living apart for a good while to make sure it sticks, or if you decide you are splitting for good, but the alcohol is no longer a factor. At that point you might do what the solicitor suggested, or some families also do one week with each parent for example, there are various possible templates for shared custody.
If you decide to split for good and the alcohol IS still a factor that will be a trickier conversation. But if you start things off this way, it becomes the status quo, and even if he was unhappy with it later and it went to court, they’d likely factor the alcohol issue into the equation and think about the children’s best interests when considering whether changes should be made at all and if so, it would usually be built up slowly over time and usually only if he is able to prove that he has managed to get on top of the alcohol problem.
You seem to be truly considering what is in your kids best interests so trust yourself as their mum to know what will work best for them right now if your husband is amenable to your suggestions. You don't have to decide how it will work forever for now, just think about what’s going to keep the kids safe and well and not expose them to unnecessary stress. And then try to come to an agreement on what that looks like for you both for the next few months. And keep it under periodic review. Don’t let anyone tell you you’re pushing your husband out somehow that’s not what this is about at all.