Herodotus 8.60

[Phoebus Apollo]

ἢν δὲ τὰ ἐγὼ λέγω ποιήσῃς, τοσάδε ἐν αὐτοῖσι χρηστὰ εὑρήσεις· πρῶτα μὲν ἐν στεινῷ συμβάλλοντες νηυσὶ ὀλίγῃσι πρὸς πολλάς, ἢν τὰ οἰκότα ἐκ τοῦ πολέμου ἐκβαίνῃ, πολλὸν κρατήσομεν· τὸ γὰρ ἐν στεινῷ ναυμαχέειν πρὸς ἡμέων ἐστί, ἐν εὐρυχωρίῃ δὲ πρὸς ἐκείνων. αὖτις δὲ Σαλαμὶς περιγίνεται, ἐς τὴν ἡμῖν ὑπέκκειται τέκνα τε καὶ γυναῖκες. καὶ μὲν καὶ τόδε ἐν αὐτοῖσι ἔνεστι, τοῦ καὶ περιέχεσθε μάλιστα·

I'm struggling to translate the bit in bold. So far I've got, 'moreover, there is this (τοδε) in them (ie the ways in which his plan will be useful)...'.
Can anyone think of a more fluent/better way of putting it?

Also, am I right in thinking the ἐν αὐτοισι in this line refers back to the ἐν αὐτοισι in the first line? ('you will find it so very useful in these respects/ways ...')

[Hylander]

Also, am I right in thinking the ἐν αὐτοισι in this line refers back to the ἐν αὐτοισι in the first line?

Yes. And the antecedent of ἐν αὐτοισι in the first line is τὰ ἐγὼ λέγω.

καὶ μὲν καὶ τόδε ἐν αὐτοῖσι ἔνεστι -- you understand this correctly. If you're aiming at fluent English, you will need to move away from a strictly literal translation. Something like: "and, moreover, there is also this advantage in my recommendations, something on which you place the highest priority, namely . . ."

Note that τόδε (as usual) refers to what follows (not what preceeded), i.e., ὁμοίως αὐτοῦ τε μένων προναυμαχήσεις Πελοποννήσου καὶ πρὸς τῷ Ἰσθμῷ, οὐδὲ σφέας, εἴ περ εὖ φρονέεις, ἄξεις ἐπὶ τὴν Πελοπόννησον.