Radica Genesis dual voltage question

[prince tomato]

hi folks,

i have some spare time on my hands and decided to tackle a new project:
make a mini Mega Drive/Genesis out of a cheap plug and play.
this Radica thing can be modded with all kinds of neat stuff
like a cartridge slot, 60hz mod (dual Xtal switch mod)
and i want to add controller ports that work with official peripherals as well.
pinouts for all of this, and even S-video are well documented,
but i am having a hard time figuring out how to supply the 2 different voltages needed.

the Radica board runs on 3.3 volts,
but Genesis carts and controllers require 5 volts to work properly.

being a mechanic, and by no means an electrical engineer my first solution to this is to put a 7805 between the DC input jack and Vin of the 3.3v voltage regulator,
supplying 5 volts to the 3.3v regulator,
AND the 5v pin of the cartridge connector and that of the controller ports.
both regulators would be sharing common GND in this setup.

or, alternatively, place a 3.3v-5v step up booster between 3.3v and the 5volt cartridge and controller pins to supply 5 volts to the that way?

i am sure though that i am creating new problems this way,
it can't be that simple, can it?

here are two places where mods like these are discussed,
and some pics of my own Radica.
if anyone knows how to supply these voltages safely,
please let me know.

http://www.sega-16.com/forum/archive/index.php/t-7673-p-5.html

https://www.elotrolado.net/wiki/Mods_Mini_Sega_Radica