Can I add weight-training to my Garmin 5K coach plan?

I got a Garmin Forerunner 45 watch and I'm doing a 5K training plan with Coach Greg.  I'm quite happy with it, but I didn't see an option to add a couple of strength-training workouts I do every week.  

So what I'm doing is that I am rescheduling the 5k workouts and doing the weight training in the rest days.  I'm training on this schedule:

1st day            running

2^nd day           weight-training 35 minutes

3^rd day            running

4^th day            Rest

5^th day            running

6^th day            weight-training 35 minutes

7^th day            running

…and so on, so I train 3 days in a row and follow with a rest day.

Am I overdoing my training?

Is there any Garmin training plan that includes weight training?

Any advice much appreciated.

Age: 57

Male

Weight: 80Kg