Avoid the 7 speed, 14-34 Shimano "Mega Range" freewheel sold by Harris Cyclery and others. It jumps from 24 to 34 teeth on the low end. If you're topping out a steep hill in the 34 shifting up to a 24 is an absurd jump. The IRD 13-32 is a better choice. It progresses from 28-32 on the low end.

http://www.interlocracing.com/freewheels_steel.html

As others have suggested, just carry the small spline tool on tour. No chain whip is required. A borrowed vise or long handle wrench from any garage should remove it. Loose and re-tighten at home before heading out if you suspect it to be frozen on.

Some day I'll upgrade to a cassette but my Phil Wood threaded hub costs $165 versus $456 for his cassette version!