Marble is difficult for a children's bathroom ...besides being slippery ...get a no skid surface for all bathrooms ...it's just safer ..it's all about colors , so keep it simple , clear see through shower curtains ..and the only color , if any should be in the towels .

P.s. Your bathroom looks nice , perhaps just paint the cabinet black

Some more pics

Top it off with a fun shower curtain

You can get a porcelain tile that looks like marble. I'd keep it on the warm side though because of the biscuit tub. These are from Tilebar.

https://tilebar.com/fortezza-calacatta-antique-24x24-porcelain-tile.html

I would stick with a wood vanity to add some warmth. Drawers for storage are always nice. I did my 30" vanity out of 2 sink cabinets-an 18" door base with a 12" drawer base. It was much more customizable that way since it let me choose color, door style, etc. and I added a quartz remnant and my own sink. I know it's a little thing, but I also replaced my toilets with toilets with sealed sides and they're so much easier to keep clean.

Good luck with your project!

Thanks Silviakunst....I hadn't thought of how slippery that flooring an be.

Thanks Radhannoo - these are some great flooring options. I would really like to great something interesting with the flooring. I will admit that I am slightly intimidated with smaller tile options because of the multitude of grout lines although I do love the hexagon mosaics.

Katinparadise - I will check out the site. Thanks

I did want to pose one more question - with a almond bath, do I need to have an almond bowl with a new countertop or can I get white?

Of course white works well !

I have a biscuit tub as well and did a white sink. It should be no issue. The tub will be covered most of the time with a shower curtain anyway.

In one house I owned I decorated a bathroom in various shades of white, cream, taupe, etc. The vanity was maple with a natural finish -- very light. By embracing the different shades of white and cream, it turned out to be a very affordable way to modernize the room. It looked wonderful. I like black with cream and white, too.

Be wary of small tile with a lot of grout on the floor. I made that mistake and have regretted it from the day it was finished. If I could do it over, and I can't, I'd use a larger format tile and minimize grout lines.

Good luck on your project!

Be sure your tile has a stone-like uneven or brushed surface to minimize slipperiness. Grout also helps reduce slipping. Then use machine-washable bathroom rugs with non-slip backing on top of the tile. Grout is not a problem for cleaning if it has been properly sealed.
As for the vanity cabinet, you may not have room for a cabinet with drawers. Each child should have a labeled lucite bin in which to keep their own supplies, and it should be stored inside the cabinet. Hooks for hanging the bath towels allows them to dry faster than when folded on a towel bar. Each kid could have his/her own color for towels and washcloths.