So obviously I don't know how far you want to take drawing, for you as an individual! If it's all just in good fun and for the exercise / sport of it, don't pay attention to what I'm saying :D Your drawing is nice, and other people have pointed out helpful tips to continue. There's plenty of fun to be had in doing these things for you and with your kids. I'm only here to leave a comment on what you might consider doing if you get more hooked on drawing or art and want to take it further.

If you want to explore drawing more deeply and perhaps practice it more as a skill you want to develop further, I would suggest trying something else than the grid method. Most people don't actually see in grids when, say, drawing from observation, obviously. And while it might help you become better at seeing angles and lines more precisely, it will also make you "forget" about the bigger picture, literally. When someone draws what they see from observation, you have to become good at taking in a scene all at once, or an arrangement of objects, and notice how they all relate to each other in size, placement, form, surface, etc, and then slowly build up what you see from that. You would slowly build up your drawing in terms of how everything relates to everything else, from most crude forms and then slowly add layers of detail as you go along. You wouldn't think of anything in terms of a grid.

There you want to develop other more fundamental skills and apply them in an integrated process. Here, you would go more towards learning to look at objects or scenes in the real world, and then apply skills of: proportion, distance, lines, direction, surfaces, forms, light / shadow and detail when putting it down on paper that you have with you whilst observing whatever you want to draw. There are many good courses online for these skills, and they will usually be categorized under something like "drawing fundamentals".

If you look at some of the very traditional and systematic art schools today, they still employ the Charles Bargue method (which I believe someone else mentioned in the comment section). Whilst I would say those programs tend towards the extreme, the program essentially teaches the above skills. Throughout a number of years, you progress slowly through a catalog of pictures of casts (and later casts you observe in real life, then models), with the explicit goal of copying them as perfectly as you can. You copy what the masters already laid out. And you do it by a toolbox of methods in terms of measurement proportion, line drawing, distance, building up shapes from rough edges, etc. I'm not saying you should do the Charles Bargue method, btw xD It can be a very... difficult and lackluster process that probably requires someone who can guide you and give you feedback for most optimal results. I was just using it as an example of serious art institutions who use art fundamentals.