Aldon is more likely to come from the English, from the German element 'ald' meaning 'old' - it led to Aldous, Alderon, etc. so Aldon ties in nicely. Eldon, maybe, but you'd have to trace and explain the switch in vowels of an established placename and surname....not as likely.
Aleda is more from Aleida, North Germany formof Adelheid, via the Low German form Aleit. The Hungarian Alida form is now used in Germany but the Aleida form pre-dates it. In modern times, both may be influential on the spelling of Aleda.
Devon