Here is a bit of advice from an art teacher who has had years of experience working with little kids.
Remember that all kids are different and you have to try different approaches to each one of them. Don't push them hard. The main idea is to have a fun time with your child and if he learns something at the end, look at it as a huge bonus! Sometimes even mixing different colors together into a big brown spot could excite a little kid, so enjoy it with him. Praise him a lot! Always have the patience to discuss what it is that your child has made. And you definitely don't have to be an artist to make these "masterpieces" with your kid. Maybe you'll learn something too.
If you have older siblings try to involve them too. They can do the same projects or more challenging ones if they want.

Before you begin - some cleaning ideas.

There are a few basic things that you can do with your little one even if he’s just 2 years old. Those are:

Hand printing

Projects for 2-3 year olds

Projects for 3-4 year olds

Projects for 4-5 year olds

Projects for 2-3 year olds

Projects for 3-4 year olds

Projects for 4-5 year olds

Home made Play-Dough

Projects for 2-3 year olds

Projects for 3-4 year olds

Projects for 4-5 year olds

Potato stamps

Easter Egg Coloring

Halloween
Thanksgiving and Fall
Christmas, New Year, and Winter
St. Patrick's Day
Easter
Mother's Day

Cleaning ideas for making your life a little bit easier:

1. Don’t throw away old shower curtains. You can spread them under the table and chairs and your floor will stay clean.
2. Use a cheap plastic table cloth or even old papers to cover the table.
3. As an art smock, give your kid a large old tee shirt.
4. When working with a group always have plenty of disposable hand wipes available and a roll of paper towels at your hand