Dewsbury - Newark Stations return:
SSR - SUPER OFFPEAK R ECC
00000 - ANY PERMITTED
1 Adult @£ 20.55 = £ 20.55
1 Child @£ 5.90 = £ 5.90
__________
£ 26.45
Standard Class Return
That seems very expensive to me!
Yes, as
ainsworth74 says, an Advance
single ticket is £11.80 (That must be the £13.20 fare in Avantix, with the EC Online discount) however that seems a very small saving when you need two of them and you lose flexibility with an Advance. In theory cheaper Advances are available but you may need to book weeks in advance for those.
There is a small saving to be had splitting at Adwick:
Dewsbury - Adwick
Anytime Day Return £6.05 for 1 FAM + 1 CHFAM
Adwick - Newark N Gate
Anytime Day Return £15.60 for 1 FAM + 1 CHFAM
Both are valid on any train and this combination totals £21.65, a saving of £4.80.
Splitting again at Retford doesn't help much; only saving 40p. Adwick/Donny - Retford, and Retford - Newark Anytime Day Returns all being priced at £7.60. Two of those is £15.20 which is 40p less than the Adwick/Donny - Newark fare of £15.60. It also limits you to trains that call at Retford.