Make your own bubble solution. You can use dish soap and water, and test it until you can blow bubbles easily.
It might be fun to put the solution in the sink and let kids blow bubbles into the sink with straws. They can watch them mount up and then pop them.
The bath could be another option for this. There are usually a lot of bubble toys at the department stores for kids to use outside.
Teach kids how each bubble almost always come out in a circle no matter what the wand is. You can even show them this as well, try different wands that would look like they should make different shape bubbles.
Use different ideas around the house for bubble blowing. You can use a lot of different kitchen supplies like spoons with holes and a whisk to do some different experiments.