First thing i'd do is plant a couple of fruit trees if there's space. They are low maintenance, you can hang swings, trapeze, hammocks from them. They look gorgeous in spring full of blossom, and there's something so lovely about picking apples or pears off a tree to put in the kids' packed lunch. Also if you hang bird feeders from them you get fantastic wildlife in the garden all year round.
They create height, give shape to the garden and tbh you can leave the rest pretty much to lawn then if you want to because fruit trees make a garden look loved. So I'd get the most mature ones you can afford, make sure they cross pollinate, read up on how to plant them so they'll establish, and that's the biggest job done.
But I'd also get some lovely climbers. Abutilon loves a sunny wall and some varieties flower for months on end. Honeysuckle smells nice, so does jasmine. These, with roses and clematis can scramble up fences and make a garden look more lived in.
Depending on your taste, some evergreen shrubs or shrubs that give winter colour can help make the garden look pretty all year round. Personal taste but I love dogwood for its bright coloured stems, blue spruce and anything with heavy winter berries, like pyracanthus and cotoneaster. Then any annuals, herbs, tomatoes etc you can grow in pots.
And if you have a sheltered spot, the most beautiful small trees or shrubs that give interest all year round with their gorgeous leaves and branches changing colour are acers. Just look up Acer or japanese maple (same thing) on a website and choose one that's the right size. I'd grow a whole forest of them if there was space.