I really dislike making a side bet on games in Colorado. Its just to easy for a team to score a lot of runs in that park. A bad hitting team can suddenly look great at Coors Field.
As far as the freeplay, unless you have a big dog you feel very confident in, why not pick a couple small dogs for 2-team parlay. That way you'll get good payout and have a better chance of hitting. There are two small dogs I like today (Cards, Astros). They are on my card (straight ML plays, no parlays).
Good luck Timmy.