With PiDome you are able to add options to device skeletons you create (so you can re-use devices). When you add a device to the server you can set these options.
Example: You have 5 temperature nodes, you create a skeleton once with your temperature node setup, you add the option poll time with a drop down choosing between 1, 5, 10 minutes (you can also use input fields off course).
When you add these devices to the server you then can set the polling time per device. By using the mysensors functionality to do a data request you will be able to get the option's value (See "Requesting data" on the API page: http://www.mysensors.org/download/sensor_api_15).
But. The above does not work yet for PiDome as this is not implemented in the mysensors plugin. Too be honest i did not even have thought about it. I have created a feature request for the mysensors plugin to have this implemented at: https://bitbucket.org/pidome/pidome-mysensors/issues/4/be-able-to-create-options-for-devices-in So if you are going to use PiDome or not, this will be implemented (so other users will also be able to use it when it becomes available).
I can not yet give an estimate on when this is implemented as the Custom devices editor is on the optimization list, and currently i'm extremely busy with the raspberry pi client to have it compatible on multiple display resolutions (starting from 240*320). You have the possibility to vote for the option so it can go up on the prio list (It is the three of PiDome deciding which option is next to pick up).
Regarding of booting all the sensors at the same time. The server does not care. It is capable of handling bulk messages from the gateway. So you need @hek to answer this one.
