gearing question how low can i go ?

mountainpenguin Posts: 37
edited February 2018 in Commuting chat
Ok so new shiny bike but gearing is way to high for its duties / my fitness.
Duties commuting and towing toddler up hills.
current gearing is 11-28 with a 54:36 up front with a ultegra short cage
I would like to keep things as light and as cheap as possible.
I gather i can buy and
to convert to a log cage.
Officially this would allow a 11-32 on the rear. unofficially how big could this get ?
could I get a 1170 11 - 36 on ?
and swap the front chainrings
or would a simpler approach be:

1. Install cassette of choice. Must be 11t high gear or it won't fit hub driver. SRAM PG-1130NX is light for 11-42
2. Install Shimano 11 spd MTB derailleur. If only going to 42 tooth rear and 1X in front can use medium cage. XT RD-M8000.
3. Install Wolf Tooth Components Tanpan SH11 This makes road bike shifter play nice with mtb derailleur. Do not need online adapter. Shorten rear cable casing. Longer rear cable needed but will usually be included with new derailleur.

and would there be any benefit to swapping the front chain rings or is 42:34 just too low ?