Our son has an early 90’s Specialized Allez Epic with 7 speed 105. He doesn’t ride very much and we have hills.
What I would do is find a 39t inner chainring. It doesn’t have to be 7 speed, it just need to have a 130mm BCD.
It is almost impossible to find a a 13-32 cassette, I built one for our son, but you can get a 12-32 7 speed cassette. The gaps are pretty huge, but for now it will give you enough low end.
Get a long cage mtb rear derailleur compatible with a 7-9 Shimano SIS. This will let you run the 32t. I used an old Deore from the 80’s.
Once you ride enough with this setup, you’ll be able to make a decision on where you want to go. If your Kestrel has 126mm dropouts you are limited.
John