Hello aabcam75;
Configuring ET200M modules as slaves to a S7-416-2DP is straightforward, using Step 7's Hardware Config. Use the Profibus-DP library to select the IM153 comm. module you are using, bring it on the Profibus line, give it a Profibus address and complete with the S7-300 I/O modules you will need. Then use the S7 addresses selected by the Hardware Config editor to access the I/O modules from your program.
What makes your request special is your use of the word "redundant"; please specify what you mean by that term, as the CPU 416 is not a redundant processor in the Siemens family (only S7-414H and S7-417H are considered redundant). Do you intend to implement redundancy at the fieldbus level, and if so, in what circumstances. Then we can talk about the How.
Hope this helps,
Daniel Chartier