Growing up in a 'Navy' town ( Annapolis, md, home of the USNA ) I saw families of friends whose father was in the Navy and during the Vietnam War, they would be gone for months . . . with only letters and VERY rare phone calls to keep in touch . . . it wasn't that the dads didn't love their wife and kids, but 'work' came first . . . a lot of the marriages didn't survive when he did get back stateside, as ( in the 60's ) it was hard for a man to accept that a woman could run a household and do all of the banking, taxes, child rearing, etc, without him . . . and jumping in and trying to 'take command' of the household didn't always go over too well.
At least Neville does get home, although he's got to learn to seperate Hogwarts and home . . . demand that he get some privacy and 'alone time' with Hannah and Gavin . . . he has to learn to say 'No'
That being said, you have several avenues you could explore; is he getting caught up in one of Harry's problems, again? Is he taking on too much, in order to keep his job/replace Professor Sprout when she retires? Does he need an assistant? Does Hannah need to get out more? Does the Wizarding world have pre-school? The idea of her re-training for Healer and applying for Poppy job when the time comes for her retirement, has merit - would Neville be supportive or slightly wary of her reasoning for doing that? ( male pride about supporting the family, etc )
I'll keep an eye out to see if you post more . . . this could get good!!!