First of all, welcome to the forum!

Get yourself some Naphtha at your local hardware or paint store for cleaning up old grease and oil.
Next get a lubricant kit like this from Labelle. https://labelle-lubricants.com/shop/kit-with-one-each-102106-and-107-for-ho-o-s-lionel-and-lgb-garden-railway-size-trains/

For the rolling stock, use a hobby knife to scrape off any accumulated dirt off all the wheels. Next use a Q-Tip dipped in the Naphtha to finish cleaning off the residue on all the wheels until they are clean metal. Clean the rollers on the loco also. Burnish the wheels and rollers with a Scotch-Brite pad until they are clean.

Next, oil all the axle bearings on the rolling stock and locomotive, and the stud the locomotive gears revolve on.

Take off the brushplates on the locomotive and tender motors and clean them, the brushes, springs and copper commutator segments on the armatures with Naphtha. Reassemble the brushplates and lightly oil both ends of the armature shaft in their bearings.

The 'E' unit may need servicing. See these video tutorials on servicing it.
Part 1
Part 2

The mechanisms on the operating cars are fairly straightforward and should pose no problems in cleaning and lightly lubing them.

Rub the tracks with the Scotch-Brite pad until they are clean, then wipe them off with a rag soaked with Naphtha to get off all the residue. Make sure all the track pins are in tight, and the track sections fit together tightly. Use a needle-nose pliers to squeeze the track ends tight if necessary.

Once the whistle tender is done, the transformer can be checked. Put the tender on the track alone, turn up the transformer and press the whistle button. The whistle  should blow. Run the trains around the track and blow the whistle again. It may need almost full power to blow with the train running. If the whistle does not blow, the whistle rectifier in the transformer may need replacing. It is available with online parts dealers.

The operating accessories may just need a good cleaning to get them working again.

For a value assessment, look up the individual items on some auction sites to give you an idea of their worth.

With a little work, you will have a nice train set to run with your family.


Larry