I'm in Bristol about 40 mins north of south Phlly. I'd suggest you join one of the 29 or so yacht clubs on the river. if you join one you belong to the whole network of clubs all the way to the Chesapeake. it's the DRYL (delaware river yachtsmens legue) There is a YC in Essington also. I belong to Anchor YC in Bristol. D R Y L Member Organizations
you must trust me on this; you DO want to belong to the YCs on the River. it's way cheaper then even the cheapist marina you will ever find. Also you will have a huge safety net!
A 25ft boat on the river will be ok The ships are not so much the problem as the big stink potters are a dangerous lot with wakes and rude navigation techniques. (them weapon, you target) Jet noise is loud but not a big problem. On the river we all take the current flow into consideration when moving up or down river. the current does run 3-7 knots. A boat with a 6knot hull speed can head into the flow and make maybe 3-4 knots. you will want a GPS too when you start using the river because you want to see the depth out of the channel. There are lots of races all up and down the river, there is East Enders YC, (racing only club) and many of the clubs have races all through the season. Ours just had one on the 10th of oct. Philly has a racing club also. Anchor Yacht Club - Home Page
Overnighting is great, again if you belong to the YCs. The river itself doesn't provide many places to anchor but there are a few. You can get to the Chessy by going down river to the C&D canal. it's not so far from philly and you can motor (with the tide) and be there in about 8hrs. Barnegat bay, shallow! need 3ft or less draft! One of the guys in my club winters his boat at Phila marine center and love it. It is $$$.
Lastly, I'd say if you can.. go bigger! the river is the place for it! and you can cruise to the Bays, or the Ocean via cape may.
PM me if you would like to vist my YC sometime.