It’s a big task. I have cut down a lot of trees, I used to have a 76 cc saw with a 21″ bar. The more I did it, the more I realized how utterly dangerous running a saw actually is. While I never lost that respect, I learned a lot about the craft.
In a small backyard you are dealing with loads of liability. For one, power lines are not only a shock hazard but also limbs can tangle into the wires. Same goes for communications lines. Then you have your home possibly, garages, neighbors, fences, dogs, all sorts of things to worry about. Strategic placement for felling a tree is really tricky. Your cuts, the weight distribution of the tree, the wind and split second timing and adjustments all come into play. It is no joke when thousands of pounds of solid wood goes the wrong way. It is terrifying.
As much as I am an advocate for doing things yourself, this is one best left to someone who does it strictly for a living. It’s not worth the liability or worse, your life. I know it’s painful to pay an Arborist, but in this case I would strongly suggest you do not undertake this unless the trees are less than 15′. Small trees can easily be wrangled so long as you are experienced with the saw and agile.