this is what will work for you:
1) Go to the store, purchase the largest boxed toy you can find
2) Drive to the nearest thrift shop, check for fabric, quilts, machines and the like.
3) Open purchased toy in the parking lot and donate it to the thrift shop as he will never play with it.
4) Take your Grandson his NEW box, and he will have hours of play time in it.
5) Use said box for fabric storage, as he will never play with that box again so you may need to repeat this process for the next 10 years or so.
ps- I heard this also works for cats and puppies! Enjoy your time with him!