Here's what I suggested:
Mon - Yoga
Tue - Walk 5mins, jog 5mins, walk 5mins
Wed - Treadmill run, 30-45mins, 1% incline, keep heart rate between 130-150bpm. Take walking breaks if heart rate goes over 150bpm.
- Spin class - wear heart monitor, anything below 145bpm is fine, but nothing over 145bpm!
Thu - Same as Tue
- Swim workout - try your best to go easy - avoid breathlessness
Fri - Active recovery…walk…light exercises if you feel like it.
Sat - 45-60mins very easy…take little walk breaks here and there so that you never get overly fatigued. Wear monitor and don't go over 140bpm, if you can hack wearing the monitor again. Otherwise, go by feel.
Sun - My first recommendation is that you do not race and instead run for an hour. However, if you are dead set on racing, go with the usual plan of a long warm-up and a slow start. Maybe see how you are feeling before deciding whether to do the race or not.