As per previous commenter, a quick floor plan would be helpful, but I'm going to take a stab at it based on what I can see from your photos:

I think your existing fixture layout is working and there aren't a lot of other functional options due to the sloped ceiling. For your vanity wall, I would suggest a new cabinet and counter that extend all the way from the left wall the right wall, in order to maximize storage and make the space feel more complete. Unframed mirrors are not terribly costly and you could have one cut to fit the entire space left above the counter and backsplash. If your kids don't seem to mind sharing a sink, I would keep a single sink centered in the vanity. This allows you to put a wide bank of drawers (or 2 banks of smaller drawers) to either side, which offers better storage than cupboards. If you are thinking of selling the home at some point, you may want to consider putting in 2 sinks, but you get less functional storage (each sink needs a certain size of cupboard to accomodate plumbing pipes) and you will also have trouble centering a light over the left hand sink. With a single sink, you have room for a reasonably wide vanity sconce, which I would mount directly onto the mirror. (Tip: a sconce with a larger base will make it easier for the contractor locate the hole in the mirror as there is more margin for error). Budget allowing, you could also think about running cabinetry straight up to the sloped ceiling on the left hand side. This would creat a small pantry-style cupboard that helps out with toiletry storage and towels.

For your tub/shower, I think your kids are at an age where a shower would suffice? I assume the shower head is located on the short partition as it's unlikely to be located on an exterior wall. So, we likely need to leave that partition in place, but you could put in a tiled shower base and get just a little more depth (try not to butt your wall tile right up against the window casing above if you can helpf it). Some clear frameless glazing would spruce things up a bit and make the space more open. Cost savings in this area would involve using an acrylic base rather than tile and using framed glazing instead of frameless. Again, if you are thinking of selling the home at some point in the near future, you should leave the tub in for potential buyers with young children. You could still use clear glazing or a shower curtain, rather than the frosted sliders.

I'm guessing with 2 kids, you could use some more accessories: a couple of robe hooks on the back of the entry door, plus another towel bar on the wall across from the door. I see that the slider handles likely double as towel bars and you can also get this style of handle for frameless glazing, if that's the way you go.

As far as asethetic style, Houzz is a great site for inspiration images. Decide if you like traditional vs. contemporary. Then pick a cabinet colour. From there, decide if you want a warm scheme (beige/gold tile and counter products) or a cool scheme (grey/blue/white tile and counter products). Try to keep your lighting, plumbing fixtures, bath accessories and cabinetn pulls of a similar style and finish.

I hope that helps; good luck with your project!