I've been 95+% in my category at DL for a year and a half.

I usually get some/most of what I want including 2 weeks weeks off in a row in both July and August the past two years it just takes a bit more effort with no seniority. At the end of the day seniority is king but here's generally what I do...

APD (one per year) and IVDs (2 per year) I save for the big stuff. APD will drop a trip or up to 4 reserve days. IVD will drop a trip or a reserve day using your future vacation.

Each month I can usually drop a few reserve days if I need...this is staffing dependent obviously. Next month there are 12 blue (positive reserve coverage) days in my category. I usually have 3 day reserve blocks so dropping one day really limits my usefulness for that block. X day swaps are also an option but again staffing dependent. I've had ok luck with this but you can't use swaps to create a work block less than 3 days (narrowbody). The day you want to work must have worse coverage than the day you want off. A few times this year I've also bid large blocks of reserve days and yellow slipped a trip that would require the company to give me my 30 hours of rest over a day I need off.

With better seniority there are other strategies you can use to not work on reserve once you get comfortable with PCS. In terms of lineholder stuff I haven't had a line since Feb so I wont go too in depth but when I was a more senior FO I would swap with the pot all the time for different days or better trips I could then post on the swap board for people to take. Swap with the pot (company trips) and the pilot swap board are lineholder only and can be valuable tools in my experience but like I said it's been awhile.

Lastly we do have a lot more sick time than other airlines and it doesn't roll over soooo.....Some bases also have state sick.

Hopefully that's somewhat helpful

Either way best of luck to you and your family!