Retrospec sells $39 cranks. Are they too weak for a summer's use? Are they good enough for street and light trail use?

Three-piece Fixed-Gear, Single-Speed, or Fixie bike forged aluminum crankset

170mm Crank Arm Length without any overlap of crank arm & chainring bolts

All New Crank Arm Design is much stronger for faster and more aggressive riding

Fits on road, mountain, fixed geared fixies, BMX, track and single speed bikes

Standard Bolt Circle Diameter (BCD): 130

Takes 9/16" pedals

Should be fine. There are adequate double and triple chainring cranks that sell in the same price range so that one should be plenty good enough.

Cool. Thanks. :-)

They're generic Taiwan-made cranks:
Mantra Cranksets $39 | Colorful Forged Bike Cranksets for Fixie, CycloCross, Road, & City Commuting Bikes | Retrospec Bicycles
You should be fine. Nice selection of colors.

The 130 BCD may be a factor if you want chain rings smaller than 39t. Also you need to check the crank arm(s) to chain stay clearance in relation to your preferred/ideal chainline.

I just want something simple like on a my old BMX bikes or something similar.

I like how they list "specifications" but don't tell you what bottom bracket spindle length is needed.

IME, correct spindle length has too many factores to allow accurate prediction of what would be appropriate.