I find this hard too, I have 3 one year olds and 2 toddlers, I usually do the bigger crafts with the toddlers while the babies have their morning nap or while they have free play. I do a lot of hand print/ foot print crafts for the babies and two simple spring crafts I did last week were cutting out flowers and letting the kids finger paint them and same with rain clouds. I give the babies sponges to paint with sometimes too. But something like rock painting I leave the babies out of it. I have started only doing one bigger craft a week and then have colouring and stamps available daily...I was trying to do a creative craft every day and found it to to be a lot of work, expensive, and no one really seemed to care...once a week it is more exciting!