I think your starting point should be the official guidelines:
These show you what you should consider when deploying an Android implementation. I am assuming from your message (maybe wrongly) that you already have some experience with DHIS2 on the server side. If that is not the case you should also review the guidelines (there are many so linking the main portal https://docs.dhis2.org/2.34/en/)
It is difficult to get from your message what will be all your needs. As the program doesn’t seem extremely confidential (maybe wrongly assumed again) I think you might want to put more efforts in making program attractive by using nice pictograms and colors than on security (in case you would need to chose one above the other, for example). Same with training, you might need to focus there if the person using the devices have never use the software before. Another key question would be: are the users of the tablets/phones going to enter data for consumption on the server or they need to get immediate feedback (i.e a child with an extremely low weight-for-age ratio should trigger something in the program so the child is given or transferred to another unit).
As a last note, take into account that having mobile devices on the field will mean the workers can use them to enter data offline; however it will mean that probably you will need to design a plan to update/maintain those devices. Here an MDM can become really handy.
Feel free to come back to the topic with more specific questions as the reply above is just a quick overview.