70mm f/10 will do fine, my main scope is a 70mm f/5.
In general the supplied eyepiece are poor expect to want more/better. At f/10 reasonable plossls should work but eye relief reduces with eyepiece focal length.
Jupiter, although low try around 50x to 70x, so a 12mm or 10mm eyepiece.
Saturn, again low, smaller, needs 100x to 120x, so 5mm, 6mm, 7mm eyepiece area. Magnification maybe hard to get.
Moon, actually much complained of by always a good default.
Next, get out and learn a few constellations and a few things in them. Targets are specified by constellation.
M13, Globular cluster in Hercules. Halfway up one side of the square, can be seen in binoculars.
M92, Globular cluster in Hercules. Difficult as it is somewhat away from the constellation stars. Have fun finding.
Albireo, color contrast double at the end of Cygnus. Follow all the way down from Deneb and the cross bit.
M33, Galaxy, should be viewable, 1 degree size so with a plossl you would need say 40x which is say a 20mm eyepiece. Your 20mm may do it.
M31, horrible to say forget it, reason is it is too big to fit all in at once. M31 is 3 degrees, that means 15x and that means a 46mm 50 degree plossl and they do not exist. Use binoculars, maybe use the scope to demonstrate the problem.
Double Cluster in Perseus, actually half way between Cassiopeia and Perseus. 1 degree so again a 20mm eyepiece, or binoculars for fun.
Find Auriga, 3 open clusters there. 2 inside Auriga and one just outside. Not sure one should be called a cluster, bit poor/pathetic.
Double double in Lyra. Pair of stars that are each a double. Think you need around 40x to split so say 50x and that makes around a 15mm eyepiece (46x).
So find: Hercules, Cygnus, Auriga, Lyra, Perseus, Cassiopeia.
And have fun buying lots and lots of eyepieces.
No worries about the 70mm, one has done me fine for 20 years.
You could go mad and buy a front solar film filter, ND5 is the specification for visual, and have a look at the sun. BUT finding the sun is not easy as aiming the scope at it can prove "difficult".
Little on the sun at present but it is another option, and can be done in the day and in the warm sunlight.