You are you as well as your other roles of father/son/brother/lover/employee etc…
While being a father is the most important thing you can be don’t lose sight of your own identity as an individual.
Your kids want to get to know YOU as well as your role as a parent, it helps them to figure out who they are too, and your relationships with others are important to them – platonic or otherwise (eventually in time), as it gives them a frame of reference so to speak. Not to say that moving on is necessary, but certainly your friendships are important to them as they can see your friends as people that are important in their lives too. I’ve had great support from friends and my son has always felt reassurance of this as he also feels there is a good network of people around. This wasn’t always the case as it was him and me against the world initially apart from family as I became very isolated at one point but this did neither of us any good.
I neglected the importance of time for myself (as in not being selfless) during the first stages (years) of my separation, and only now begin to realise the importance of your child seeing your life and wanting to become part of it as well as you being a parent to them. Recently I rekindled an old hobby (climbing/bouldering) after my son said he wanted to try and we both did it together and loved it. It’s important to enjoy things WITH them not just doing things FOR them. They see you as a reference point for everything and that includes how to be happy and how to have fun. This can be as simple as going through your old record collection together and showing them things you used to do as kid but to be able to enjoy those hobbies and show them good social interaction is important. It can be extremely difficult at first and I must admit I am an introvert by nature but to try and overcome this is well worthwhile, and it is a case of taking the first step.
My children are older all over the age off 10 i think welshdad is right. It can be hard to try and find friends but are you able to take them to some kind off activity where you can meet others. Is there a local gingerbread group in your area? I myself would like to find one.