First Class Award travel question

If the answer to my query is in another thread, I'd appreciate a link.

I'm going to be booking an award ticket for my aunt, from YWG to ATW thru MSP (as the only one-stop option) flying in April. Dates are totally flexible. Of course, I'd like to get away with spending as few miles as possible, but in the end, that is the least of my concerns.

The MSP-ATW/ATW-MSP segments are always on CRJ100, but the YWG-MSP/MSP-YWG segments I'm looking at are Embraer 170 or 175. I'd like to book my aunt into First for these segments outbound and return, even though, yes, is a short flight.

So, my problem. I search for First/Business award travel flexible dates. Sometimes on the outbound, First comes up for these E170/175 flights, but sometimes, even though searching for First, it lists only economy. Regardless of low/med/high award.

Then, no matter what, both return flights, even the E170/175 segment, list as economy, with no option for First.

Am I doing something wrong (as this is my first attempt at booking award travel with Delta)? Is this better done with agent? Am I asking for the impossible, and there really never is an option for First on the return MSP-YWG?

Insight from the FT experts would be greatly appreciated. :)
Doris