Playing 2 games in 1 week

depends on your numbers, we play our jv games on Monday and varsity Friday, was in a conference that played their jv games Thursday and then varsity Friday, so if those kids could handle it I say 2 days rest is better than nothing schedule your frosh on ofriday with varsity then soph on monday

First off, how many kids do you have in your program? Most mid to large size schools I've been at (1300+ student body) keep all the freshman together (none of them go up to JV). So yeah your Frosh team tends to be larger, and in a lot of ways better; but I think it has some value.

That being written I am at a very small school right now (260 student body) our program top to bottom will have maybe 40 kids and we have two teams (varsity and jv). Those kids who play jv (usually 20-25) will also suit up for varsity, most as just-in-case backups. A handful of these jv players will play on a couple special teams, and a few will see significant snaps (over 20) in the varsity game. All of our varsity games are on Friday, our jv games are usually Thursday with some Saturdays.

In the end we tell these kids its just the nature of things; ice, hydrate and fight through it, we are a small school and this is what we have to do. I went to a new HS when I was in school, so I remember being in a similar situation my Soph. year.
As it is we have 3-4 kids this year who will be "swing-players" and see significant time on both levels; we try to monitor what they do in lower level games, and will substitute when we see necessary.

that days seem dangerous

and I could see where a lawyer could have a field day with that

football is different all over the country, nothing like that here
all freshman games are thursdays and you can only play 1 game per week

In our state no player can participate in more than one game in five consecutive calendar days, and no more than nine games in a season (not including playoffs).

Unless facilities are an issue (shared), most schools play Sub-Varsity games on Thursdays, Varsity on Fridays.

We had the same situation due to weather concerns. Ironically, we won both games. Then the following week we got absolutely destroyed. I really felt like their was some "hangover" since it was our 3rd game in 12 days. 

Tough situation. 

Also have done two games in one week and it's a pain. Another school had the advantage of scouting us when we played on a Monday night, and we had to turn around and play them on Friday. We weren't very good anyways, but they were one step ahead all night long.