I am by no means the expert on here, but I think it depends on frequency. If you are running twice a week, then you have plenty of recovery time in between so I would increase the intensity/speed for for those two 5ks. You are maximising the time you are running, burning more calories, using more muscles fibres, engaging your nervous system etc - all benefits.
My advice would be to try and add another run and include some variety. I don't enjoy running at all, but am in a place now where I run most days - including a quicker short run, mediums distance, long distance, and then a few filler runs depending how my body is feeling, so usually anything between 3 - 5 miles at a comfortable to medium intensity. Always dread going out, but feel loads better when I am back.
Maybe set an aim to try to incrementally increase your pace per mile, so you are gradually increasing your speed? It will get uncomfortable but at least you then know you are pushing yourselves to a new level. Even if you don't manage to increase the pace for each mile, even if you do for one and maintain your usual for the others then it is progress!
Another general tip; vary your route. That is the only interesting and "fun" bit for me - planning and running a new route/section/combination of previously used routes. It helps keep it fresh.