My girls have the same age difference.. It was hard. I'll admit now that they are 3 & 5 it's easier... Here's some things that might help.
Coloring~ I put a plastic table cloth down and held my little on while the older one worked indepentantly.
Play-doh~ same thing
Puzzles~ we would all sit down on the floor, I had peg ones when they were little and then graduated up based on skill.
Blocks~ we would all sit down on the floor my little one would chew on them while big sis would stack them up then little on would knock over.
Shape sorter~ It's fun to watch the younger ones watch and then one day be able to do it themselves.
Read~ We read a ton of books everyday and still do.. My 3 yr old read a book the otherday.. all memorized of course but that's how many time shes heard it.
Before the preschool days started, we would get up eat breakfast, get dressed play together for a couple of hours, then the little one was ready for her morning nap. While she was napping I had time to spend with my older one. On the days she wanted to play independantlly I was able to get things done or get on here
After nap time we would play, read until lunch time. After lunch I allowed them one show - My girls didn't know their shows were on TV.. I had movies for them, when it was over it was turned off. They didn't know they could watch it all day
Somehow everyday, dinner got made, the house got picked up and laundry was done.. I would just take the 5 minutes I had to get something done. Clean the toilet, change a load of wash.