Firstly, welcome to the forum.

Well done for wanting to set up in advance - so many people don't do that, so it's refreshing to hear you are planning.

Since you have an exoterra, I'd recommend getting the 18" Exo terra light top and putting two 6500 or 6700 K bulbs in it (natural light colour and ideal for plants). Since you say it's 70 F at night, two 20 or ~25 watt CFL (compact fluorescent) bulbs would be able to heat it and light it during the day.