I wouldn't start all your seeds at once. I usually sow tomatoes and peppers (as well as things like courgettes) over a period of about 4-6 weeks. That way they don't all crop at once and you have the advantage that if one batch fails due to temperature, light, water, cat sitting on them, etc. you haven't lost everything for the season. You can also experiment as to when things grow best for your area, although this may change from year to year depending on conditions.