Your little grandson is like my great nephew. He loves to chase bugs and one day he saw a frog in the yard and chased it till he caught it. He still has it. His Mom bought a terrarium and got moss, rocks, etc. and put the frog in it. They buy crickets to feed the frog. One day he was playing the yard and a neighbor ask him if he would like to have a ferret. He ran in and asked his Mom and the rest is history. They have a zoo now. Ferret, frog, puppy, guinea pig. I made him a quillow (a quilt that folds up into a pillow) out of frog fabric and he loved it. He says he wants to be a veternarian when he grows up.
I know your little one will love this one.