Get the largest vanity that will fit. Racks over the toilet. Here is my very small guest bath in my Florida home. That bottom drawer hold 8 hand towels. We have a linen closet down the hall from this bathroom. When we bought this home, the previous owner had two towel barson the door plus a small one over the toilet. We didn't find this necessary but it's like storing towels in plain sight. Also notice we chose a left offset sink.

Figure out what really needs to be stored in the bathroom and what can be moved to other areas of the house. The sink is not pictured but if the sink is a cabinet consider moving most storage under there and install pull out tiered shelving in cabinet to maximize space and make retrieval easier. A hand towel over the toilet gives me the heebie-jeebies yucky ! As noted in photos below move the light to above the mirror and have mirror same width as sink to feel more expansive. You could also do the whole space with a mirrored cabinet vs a mirror and cabinet so its one cohesive expanse doing a mirror and a cabinet may be choppy

If they would each be the size of the standard 5x7 bath that used to serve as the only full bath in the house, and it has no negative affect on your budget to have another or negative effect on the bedroom size it would be fine to have two individual baths. If they would end up being cramped or shrinking the bedroom, maybe not. It's not so much that smaller bathrooms are that much more difficult to use, it's that they are a pain to clean. You could also do one ensuite and one hall access...and by the time the older one leaves the younger could move into that bedroom. I would not do a single Jack and Jill or the two sink thing. There are differing parenting styles too, and I know some parents more or less stay out of their teenage kids rooms, so it's possible that ensuite bathrooms in that situation would get really dirty. I once stayed overnight in a guest room last minute that was jack and jill with a kid's bedroom, (kid home) and they had me use the ensuite bathroom in a different kid's bedroom who was gone over that night or two. And the ensuite bathroom was not exactly filthy, but it was not clean or taken care of by a long shot. And they didn't know because they stayed out of their kid's rooms.

I am planning to get 3 bathrooms renovated in my home. I am looking for storage ideas in the bathroom. Do any of you have a small linen closet, open shelving space, or free-standing cabinet in your bathrooms? I will appreciate it if any of you can share the pictures of the storage ideas in your bathrooms. Any help will be appreciated. TIA.