I’m glad to hear the book inspired you.
Depending on your goals and how complex you are wanting to get, there are many options. Assuming you just want to get some diversity into the property and add value, I would pick some trees from the other stratum levels and integrate them.
Since you have the guavas already established, you’ll have to be creative with your spacing. You’ll also need to do a heavy pruning of the guavas (apical cuts) when you plant the new trees, otherwise the mature trees will suppress their growth.
Guavas are medium stratum, so you can add some coffee or cacao as a low tree, then some high trees (jackfruit, mango, avocado, etc) and some emergent trees. You may also want some trees just for biomass that you would keep real short by pollarding (moringa, gliricidia, inga, albizia, etc). The branches from these trees make super fertile mulch and will help stimulate growth every time you cut them. After your bananas are done, remember to take the pseudostems, cut them lengthwise and place them around the trees that need fertility.
I highly recommend checking out these other English resources on syntropic farming, especially the practical manuals, especially “Agroforestring the world from tractor to machete”. There are some good lists of trees there to help you make choices: http://adam.nz/syntropy?fbclid=IwAR04e321jvSZgGv93I0zDKXCwyayVdwL5sCY5LLaYBoSJLkxo9WPVTvZqz0
Also you may enjoy joining this facebook group. The members are really active and I’ve learned a lot from them. https://www.facebook.com/groups/387002598385226/. I know for sure of at least one other guy from the Philippines who has posted there. Consider connecting with him and sharing ideas.
Lastly, I want to make a disclaimer about myself. Even though I have a good handle on the principles, I have a lot to learn about the practical management. In a few weeks I’ll be making my first visit to Brazil and will be working on some more mature farms. I’ll keep sharing whatever I learn in the guidebook, so check back for updates occasionally. This will probably be a work in progress indefinitely.
Best wishes with your project.