Plants for Gravelled Area with Foot Traffic?

Question:We are just converting the childrens' old play area to a gravelled patio.

Most of the planting will come from purpose made boxes attached to the fences and mixed terracotta tubs so I am not too worried if they are flowering plants or not.

The gravelled area itself has weed barrier mesh beneath and small paving slabs placed randomly amongst the gravel. I want to introduce some low key plants amongst the gravel and paviours to add some interest BUT

I need something that is resistant to and doesn't interfere with, foot traffic, that has a bushy compact habit (no more than 10cm x 10cm and is perennial/evergreen.

Answers:
Sorry but your situation is beyond my scope. I will be interested in hearing other answers. You have gravel, foot traffic, a weed barrier, etc! You need a plant that needs no roots, no water, no nutrients, and can withstand foot traffic.
To withstand foot traffic conditions you would use a turf grass, however, never in these conditions. Evergreen or perennial with gravel, no chance of root development, etc. has less chance than turfgrass which is going to need six inches to even establish.
I would use the above ground plantings/boxes you already have. Design a walkway that outlines the borders with those units. Build above-ground planters that border both sides but highlight your established planter units. On the outside of the walk they need not be more than two foot tall. In those you place your evergreens.
In these planters you place your perennials and evergreens that are compact. Use seasonal plants to make it interesting. I would use, depending on your sun location, DayLilly, Cranberry Cotoneaster, Blue Fescue Grass, and Heather. The DayLilly for spring to fall bloom, the Cotoneaster for spread and berry in winter, the Blue Fescue for year round blue and mound shape, the Heather for winter color and evergreen (it blooms in winter!). All are cheap and are hardy!
Unless you are using Astro-Turf over the gravel I can truly think of nothing that will meet your needs or expectations for a full season. Removing the gravel and barrier will still not get you the walk of perennials (less grass) or evergreen to meet you needs.
Sorry, but I hope it helps. I am at gjgjobs@yahoo.com. Your question and attempt has made my mind go into a what if mode.