I use Rubbermaid bins for sensory inside ~ I have two sizes the 'under the bed giftwrap' size that two to four can fit around either on the floor or standing at the child size table depending on how well they play together as well as I use the 'shoebox' size for individual bins for things like goop and so forth because it helps to contain that kind of mess when you are playing 'alone' in it verses as a group where sensory can get silly

Inside I tend to stick to water play and save the sand for the PARK to be honest cause I do not want it in my house ruining finish on my floors and I do not want it in my yard killing my grass cause sand is insidious and even when they 'try' to keep it in a bin it migrates At the park I can shake them off and have them empty their shoes when it is time to go and therefore do my best to leave it there and whatever is missed tends to 'fall off' during the walk home!

For 'dry' sensory options instead of sand in the house I use things like pom poms, paper clips and pipe cleaners, acorns & pine cones & sticks and so forth ~ stuff easy to pick up and put back in should it find its way out of the bin Outside I use raw noodles or colored rice or in the spring potting soil and the bins stay on the deck so that it can be swept up and if it falls between the deck cracks no big deal.